Controlling instability in gacS-gacA regulatory genes during inoculant production of Pseudomonas fluorescens biocontrol strains.

Duffy BK, Defago G.

Phytopathology Group, Institute for Plant Sciences, Swiss Federal Institute of Technology, Zurich, Switzerland. [email protected]

Secondary metabolism in fluorescent pseudomonads is globally regulated by gacS, which encodes a membrane-bound sensor kinase, and gacA, which encodes a transcriptional response regulator. Spontaneous mutation in either gene blocked biosynthesis of the antimicrobial compounds hydrogen cyanide, 2,4-diacetylphloroglucinol, pyoluteorin, and pyrrolnitrin by the model biocontrol strain Pseudomonas fluorescens CHA0. Spontaneous mutants also had altered abilities to utilize several carbon sources and to increase medium pH compared with the wild type, suggesting that gacS and gacA influence primary as well as secondary bacterial metabolism. Inoculant efficacy for biocontrol was significantly reduced by contamination with regulatory mutants which accumulated during inoculum production. Spontaneous mutants accumulated in all 192 separate liquid cultures examined, typically at a frequency of 1% or higher after 12 days. During scale-up in a simulated industrial fermentation process, mutants increased exponentially and accounted for 7, 23, and 61% of the total viable cells after transfer to 20-, 100-, and 500-ml preparations, respectively. GacS(-) and GacA(-) mutants had identical phenotypes and occurred at the same frequency, indicating that the selective pressures for the two mutants were similar. We developed a simple screening method for monitoring inoculant quality based on the distinctive appearance of mutant colonies (i.e., orange color, enlarged diameter, hyperfluorescence). Mutant competitiveness was favored in a nutrient-rich medium with a high electrolyte concentration (nutrient broth containing yeast extract). We were able to control mutant accumulation and to clean up contaminated cultures by using certain mineral amendments (i.e., zinc, copper, cobalt, manganese, and ammonium molybdate) or by diluting media 1/10. Spontaneous mutants and genetic constructs had the same response to culture conditions. Zinc and medium dilution were also effective for improving the genetic stability of other P. fluorescens biocontrol strains obtained from Ghana and Italy.

PMID: 10919762 [PubMed - indexed for MEDLINE]

Relationships between acid-soluble thiol peptides and accumulated Pb in the green alga Stichococcus bacillaris.

Pawlik-Skowrońska B.

Institute of Ecology, Polish Academy of Sciences, Experimental Station, Niecala 18/3, 20-080, Lublin, Poland

Stichococcus bacillaris, an ubiquitous green microalga accumulated inorganic lead (Pb) from aqueous solutions extra- and intracellularly. In response to Pb uptake acid-soluble thiol peptides (glutathione - GSH and phytochelatins - PC) were synthesized. The proportion of the intracellular Pb uptake by algal cells was low and comprised only 3-6% of the total metal sorption. The intracellular uptake was dependent on external Pb concentration, time of metal exposure and cell metabolism. Pb accumulation in alga was determined by means of 210Pb radiometry. Reduced GSH and PC were determined in algal cells using HPLC with the post-column derivatization with Ellman's reagent. Within the studied concentration range 0.1-20 microM, inorganic lead caused a significant production of induced thiol peptides: PC (n=2-4) and some other unidentified oligopeptides, probably (GluCys)n. The time of appearance and the concentration of individual oligomers of phytochelatins were dependent on the external Pb concentration and time of metal exposure. In algal cells exposed to Pb, significant changes in the GSH level accompanying the formation of the induced thiol peptides were also observed. The GSH level decreased in the cells exposed to the lower (up to 10 microM) studied Pb concentrations or increased in the cells treated with higher (20 microM) Pb concentrations. The thiol groups originated from induced peptides (mainly phytochelatins) followed a stoichiometric relationship 2:1 to the intracellular Pb amounts, however, only at the lowest studied external concentration (0.1 microM). At higher concentrations (up to 2.5 microM), intracellular Pb concentration was equal or even exceeded (at Pb>2.5 microM) two to three times the level of induced thiols. S. bacillaris accumulated intracellularly by 46% more Pb in light than in dark and the level of induced thiol peptides was significantly higher in the cells exposed to Pb under illumination. The rapid formation of these peptides in S. bacillaris in response to Pb, and their elimination (by about 90%) when algae were placed into the Pb-free solution reveal a tight regulation of GSH and phytochelatin pools in the algal cells exposed to toxic metals. The obtained results suggest that both PCs and GSH are the primary line of defence against the Pb toxicity. Additionally, the induced thiol peptides in S. bacillaris could be a good indicator of intracellular Pb availability and stress at the metal concentrations found in polluted fresh waters.

PMID: 10958956 [PubMed - as supplied by publisher]

Effects of Ca2+ on phytoalexin induction by fungal elicitor in soybean cells.

Stab MR, Ebel J.

Biologisches Institut II der Universitat Freiburg, West Germany.

A glucan elicitor from the cell walls of the fungus Phytophthora megasperma f.sp. glycinea caused increases in the activities of the phytoalexin biosynthetic enzymes, phenylalanine ammonia-lyase and chalcone synthase, and induced the production of the phytoalexin, glyceollin, in soybean (Glycine max) cell suspension cultures when tested in culture medium containing 1.2 mmol/liter Ca2+. Removal of extracellular Ca2+ by treatment with ethylene glycol bis(beta-aminoethyl ether)-N, N'-tetraacetic acid followed by washing the cells with Ca2+-free culture medium abolished the elicitor-mediated phytoalexin response. This suppression was largely reversed on readdition of Ca2+. Elicitor-mediated enhancement of biosynthetic enzyme activities and accumulation of glyceollin was strongly inhibited by La3+; effective concentrations for 50% inhibition were (mumol/liter) 40 for phenylalanine ammonia-lyase, 100 for chalcone synthase, and 30 for glyceollin. Verapamil caused similar effects only at concentrations higher than 0.1 mmol/liter, whereas trifluoperazine and 8-(diethylamino)-octyl-3,4,5-trimethoxybenzoate did not affect enzyme induction by the elicitor in the concentration range tested. Uptake of alpha-amino isobutyric acid into soybean cells, which was rapidly inhibited in the presence of the glucan elicitor, was not affected by La3+ nor was uptake inhibition by the elicitor relieved by La3+. The Ca2+ ionophore, A23187, enhanced phytoalexin biosynthetic enzyme activities and glyceollin accumulation in a dose-dependent manner, with 50% stimulation (relative to the elicitor) occurring at about 5 mumol/liter. The results suggest that the glucan elicitor causes changes in metabolite fluxes across the plasma membrane of soybean cells, among which changes in Ca2+ fluxes appear to be important for the stimulation of the phytoalexin response.

PMID: 3116938 [PubMed - indexed for MEDLINE]

Accumulation of protoporphyrin-IX by the chlorophyll-less y-y mutant of Chlamydomonas reinhardtii.

Nicholson-Guthrie CS, Guthrie GD.

A pigment accumulating in a Mendelian mutant (y-y) of Chlamydomonas reinhardtii, which has essentially no chlorophyll and lacks inner chloroplast membranes in the light and dark, was isolated and characterized. It was identified as protoporphyrin-IX (PROTO) by spectral analysis using two different methods of extraction and fractionation. The amount of PROTO was estimated to be 10(7) molecules per cell. Since PROTO was the only intermediate of chlorophyll biosynthesis that accumulated, we conclude the y-y lesion in the pathway is after PROTO.

PMID: 3813551 [PubMed - indexed for MEDLINE]

Determination of cadmium partitioning in microalgae and oysters: contribution to the assessment of trophic transfer.

Ettajani H, Berthet B, Amiard JC, Chevolot L.

CNRS, ISOMer, SMAB, Service d'Ecotoxicologie, Nantes, France.

Alternative methodologies have been applied to the study of cadmium transfer in a food chain: water, microalgae (Skeletonema costatum and Tetraselmis suecica), oysters (Crassostrea gigas). The potential bioavailability of Cd in organisms was assessed through partitioning at the cell or tissue levels, and the predictive value of this method was evaluated by determining directly the metal transfer in an experimental food chain model. Cd concentrations were lower in S. costatum than T. suecica, in controls as well as in contaminated algae. In both algal species, Cd was firmly bound to the cell wall or had entered the cell. Cytosolic Cd was bound to intracellular ligands, the biochemical characteristics of which were not consistent with the hypothesis of detoxification via phytochelatins. In both algal species, Cd was predominantly present in the insoluble fraction, but at pHs such as those existing in the digestive tract of bivalves, it was easily extracted from the cells. Thus, exposure to Cd through phytoplanktonic food induced a significant uptake of this metal in soft tissues of bivalves. Due to the difference in Cd accumulation in algae, Cd doses associated with S. costatum were lower than those bound to T. suecica. Moreover, oysters retained a lower percentage of the metal associated with S. costatum compared to T. suecica (9 and 20%, respectively, after 21 days of exposure). Cd doses potentially available to oysters exposed directly in sea water were considerably higher, and direct uptake induced the highest levels of Cd incorporation but only 2% of dissolved Cd was actually retained by oysters over 21 days of exposure. In the soft tissues of oysters, Cd was distributed equally between soluble and insoluble fractions. Cytosolic Cd was present predominantly in the heat-stable fraction and mainly bound to compounds of molecular weight equal to 13.5 kDa. Moreover, a positive correlation was observed between metallothionein-like protein (MTLP) levels and gross concentrations of Cd in the soft tissues of oysters. These data are consistent with the hypothesis of an important role of metallothioneins in Cd metabolism in oysters and suggest a potential availability of MT-bound fraction of Cd to the consumers. These data are in agreement with the response of oysters exposed to Cd in the field.

PMID: 11243323 [PubMed - indexed for MEDLINE]

Ecotoxicity of contaminated suspended solids for filter feeders (Daphnia magna).

Weltens R, Goossens R, Van Puymbroeck S.

VITO-Flemish Institute for Technological Research, Department of Environmental Toxicology, Boeretang 200, B2400 MOL, Belgium.

It is generally assumed that the dissolved fraction of a toxic substance in surface water is mainly responsible for toxicity to aquatic organisms. However, toxic compounds are often adsorbed or chemically bound to suspended particles in the water column, depending upon the physico-chemical conditions. In the present study potential adverse effects to filter feeding organisms by metal contaminated particles were investigated. In our hypotheses the adsorbed metals might desorb in the gastrointestinal tract-due to different physico-chemical conditions-and exert toxic effects. Clay and sand particles, algae and organic material (peat) were artificially contaminated with cadmium and zinc. The contaminated materials were resuspended in standard conditions and toxicity was measured for the water flea Daphnia magna (mortality at 48 hours). As a reference, supernatant solutions were used containing the same concentration of dissolved metal as the suspensions. It was also established that the test concentrations of solid material (250 and 500 mg/l uncontaminated particles) did not cause any mortality within 48 hours. Daphnids are filter feeders: they filtrate large amounts of surrounding water, redrawing particles as a food source. Results strongly indicate that contaminated particles threaten the health of these particle-feeding organisms. Compared to the reference severe acute toxic effects were seen and cadmium accumulation was increased when contaminated solid material was present. Results were essentially the same for the different materials used in the experiments, except for sand contaminated with cadmium. This shows that mineral as well as organic materials can contribute to the particle bound toxicity. Different results were obtained when a static set up was used instead of a flow through set up, illustrating that the route of administration is important to make particles available and thus to evaluate their toxicity. Contaminated particles clearly have toxic potency, not only because they are a continuous source of dissolved xenobiotics, but also because the particle bound fraction can become available within the body of particle feeding organisms. This could lead to unexpected high tissue concentrations. More insight is needed to predict the bioavailability of adsorbed pollutants. Results of this study already indicate that suspended solids should be considered as a separate compartment in risk evaluation of chemicals, effluents or natural surface waters.

PMID: 10948281 [PubMed - indexed for MEDLINE]

Experimental kinetic rates of food-chain and waterborne radionuclide transfer to freshwater fish: a basis for the construction of fish contamination charts.

Garnier-Laplace J, Adam C, Baudin JP.

Institut de Protection et de Surete Nucleaire, Departement de Protection de l'Environnement, Laboratoire de Radioecologie Experimentale, centre de Cadarache, Bt 180, BP 1, 13108 Saint Paul lez Durance Cedex, France.

A standardized procedure is proposed to obtain from laboratory experiments the kinetic accumulation and release rates necessary to calibrate dynamic models to quantify radionuclide direct and trophic transfer in fish. The model takes into account the food-chain effect, the feeding rate, and the growth of organisms. It takes as examples (54)Mn, (60)Co, and (137)Cs transfer dynamics through a simple pelagic food-chain (phytoplankton, zooplankton, prey fish, and predator fish). The estimated kinetic rates used in quantifying all the transfers of the three radioactive pollutants through the pelagic food chain are compared from the radioecological point of view. For fish, comparison was based on the calculation of concentration factors referring to direct transfer from water and trophic transfer factors. For the prey fish and the predator fish, direct transfer gave the following order for accumulation (60)Co < (137)Cs < (54)Mn. Values reached at equilibrium in L/kg WW were respectively for the prey fish and the predator fish: 8.7 < 27.4 < 107 and 4.14 < 6.59 < 13.4. For the trophic route, (137)Cs is the most accumulated (TTF(eq) = 0.485 in 291 days for the prey fish and TTF(eq) = 1.45 in 17 years for the predator fish). A sensitivity analysis adapted to the case of a chronic contamination scenario of a watercourse was run. It showed that the phytoplankton biomass, the contact time of these drifting particles from a release point to the station where they are ingested and the feeding rates of the fish are the most influential parameter with regard to the concentration in fish, whatever the trophic level. Contamination charts are constructed for the predator fish to illustrate the relationship between the most influential ecological parameters and the radionuclide concentration in fish for simple contamination scenarios. They are shown to be effective tools for helping in the choice of the most relevant value of aggregated concentration factors (ACFs: radionuclide concentration ratio between the organism and the water, referred to steady-state and to all possible transfer pathways) for a given key ecological situation in a given ecosystem. An example is given of a simple chronic release scenario of 1 Bq/L and a phytoplanktonic bloom period. For (137)Cs, the ACF increases with increasing contact time and increasing feeding rate, to nearly 550 L/kg WW at equilibrium. For (54)Mn, ACF reaches 65 L/kg WW. For (60)Co, the general pattern of the relationship is due to the rapid kinetic rates governing the distribution of the radionuclide between dissolved and solid (phytoplankton) phases with a maximum value for ACF of 7.2 L/kg WW for the case study. Analysis of these charts provides a basis for overall guidelines for chronic releases in a given watercourse.

PMID: 10871415 [PubMed - indexed for MEDLINE]

Metal accumulation in a biological indicator (Ulva rigida) from the lagoon of Venice (Italy).

Favero N, Cattalini F, Bertaggia D, Albergoni V.

Department of Biology, University of Padova, Via Trieste 75, 35121 Padova, Italy.

Ulva rigida (C. Agardht) was collected from the Palude della Rosa (lagoon of Venice), a particular area characterized by a salinity gradient, from December 1991 to June 1993. Metal contents (Al, Mn, Fe, Cu, Zn, Cr, Co, Ni, Cd, and Pb) were determined by atomic absorption spectrophotometry and statistically analysed for differences between months and sampling sites. The mean seasonal variability is very significant (p < 0.001) for all studied metals. Seasonal trends are comparable for groups of metals according to possible functional similarities. A significant positive correlation was calculated for the pairs Fe-Al and Fe-Pb. Mechanisms regulating metal uptake are discussed, particularly the role of Fe and its linear relationship with Al. Metal concentrations in relation to salinity also were studied. Larger amounts of Fe, Zn, and Cd accumulated in correspondence of lower salinity, may be owing to both higher metal activity and burden of bioavailable metals in freshwater flowing into the Palude. Calculation of concentration factor (CF) indicates that U. rigida specifically accumulates Fe. CF linearly correlates with dissolved metal concentrations, suggesting that U. rigida is a good bioindicator of metal bioavailability, although seasonal active accumulation occurs in some cases (Mn). Metal concentrations determined in this macroalga support the conclusion that the studied area is rich in bioavailable Fe and poor in toxic metals. In any case, a great affinity for Al in U. rigida may be proposed.

PMID: 8687985 [PubMed - indexed for MEDLINE]

Patterns of metal accumulation in Laminaria longicruris from Long Island Sound (Connecticut).

Shimshock N, Sennefelder G, Dueker M, Thurberg F, Yarish C.

Department of Ecology and Evolutionary Biology, University of Connecticut, Stamford 06903.

Laminaria longicruris de la Pyl. samples were harvested from Long Island Sound (Connecticut) from January 1985 to January 1986. Cadmium and copper content was determined by atomic absorption spectrophotometry from four tissue types; young blade, old blade, young stipe and old stipe. The results were statistically analyzed for differences in both type and age of tissue. Concentrations of cadmium were consistently lower than copper concentrations for all months and all tissue types. Statistically significant differences (p greater than 0.05) were found between the four tissue types for copper in the months of March, June, July, October and December, and for cadmium in the months of February, March, June, July, October and November. Young blade tissue and young stipe tissue were the tissues which most frequently found to be statistically different from the other tissues. Young stipe tissue had the lowest trace metal concentrations (1.3 mean ppm, dry wt. Cu, 0.22 mean ppm, dry wt. Cd). Young blade tissue had significantly higher metal values in comparison to the other tissues for the months of June and October. Old tissue of L. longicruris is the most suitable for use in biomonitoring of trace metals due to the relatively little variation in metal content that was found throughout the study period.

PMID: 1616316 [PubMed - indexed for MEDLINE]

A method for assessing chronic effects of toxic substances on the midge, Paratanytarsus parthenogeneticus-effects of copper.

Hatakeyama S, Yasuno M.

A method was developed for the assessment of the chronic effects of copper on midge larva. Growth and reproduction of the midge was related to copper concentrations greater than 0.08mg/L; 50% reproductive impairment was apparent at a copper level of 0.37 mg/L. Growth and amount of food uptake by larvae were inversely related to copper concentration. Accumulation of copper in green algae was proportional to copper concentration in the water.

PMID: 7325689 [PubMed - indexed for MEDLINE]

Toxicity and bioaccumulation of cadmium in the colonial green alga Scenedesmus obliquus.

Cain JR, Paschal DC, Hayden CM.

A laboratory investigation was conducted to study the extent and efficiency of cadmium bioaccumulation in Scenedesmus obliquus by subjecting this alga to varied sublethal Cd concentrations. The influence of cell population age on Cd bioaccumulation was also studied. Under the experimental conditions employed, growth was not significantly affected by Cd concentrations ranging from 0.01 ppm to 1.00 ppm. At concentrations above 1.00 ppm, however, growth was inhibited markedly. Increases in external Cd concentration caused an increase in total bioaccumulation over the entire range of concentrations, which did not significantly affect growth. Efficiency of Cd bioaccumulation was also concentration dependent, but maximum accumulation efficiency occurred in a medium with a Cd concentration lower than that medium in which maximum total bioaccumulation occurred. Age of the cell population influenced the extent of Cd bioaccumulation. Rapidly growing, young cultures accumulated less Cd than older cultures approaching stationary growth phase.

PMID: 7369788 [PubMed - indexed for MEDLINE]

Export of Na+ from cells of the halotolerant microalga Dunaliella maritima: Na+/H+ antiporter or primary Na+-pump?

Shumkova GA, Popova LG, Balnokin YV.

Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, Moscow, 127276, Russia.

Transport of Na+ and K+ ions through the plasma membrane of intact cells of the halotolerant microalga Dunaliella maritima Massjuk was studied. Ion fluxes through the plasma membrane were induced by hyperosmotic shock (uptake of Na+ by the cells is transformed into extrusion of Na+) or by addition of K+ to a suspension of K+-deficient cells (uptake of K+ by the cells is associated with extrusion of Na+). The pathway of Na+ extrusion from the D. maritima cells does not depend on the direction or value of the proton gradient on the plasma membrane. In particular, the efficiency of Na+ extrusion was not changed at extracellular pH values varying from 6.0 to 8.0. The protonophore carbonyl cyanide m-chlorophenylhydrazone (CCCP) (20 microM) and the H+-ATPase inhibitor N,N-dicyclohexyl carbodiimide (DCCD) (25 and 100 microM) inhibited accumulation of K+ by the cells but did not influence Na+ extrusion. Significant acidification of the medium did not induce a net current of Na+ from the cells through a Na+/H+ antiporter. The data indicate that the Na+/H+ antiporter of the plasma membrane of D. maritima is not responsible for Na+ extrusion from the cells. These results can be explained by the involvement of a primary electrogenic Na+ pump (a Na+-transporting ATPase) in Na+ transfer through the plasma membrane of this alga.

PMID: 11002184 [PubMed - indexed for MEDLINE]

Plasma membrane electron transport coupled to Na(+) extrusion in the halotolerant alga Dunaliella.

Katz A, Pick U.

Department of Biological Chemistry, The Weizmann Institute of Science, 76100, Rehovot, Israel. [email protected]

The halotolerant alga Dunaliella adapts to exceptionally high salinity and maintains low [Na(+)](in) at hypersaline solutions, suggesting that it possesses efficient mechanisms for regulating intracellular Na(+). In this work we examined the possibility that Na(+) export in Dunaliella is linked to a plasma membrane electron transport (redox) system. Na(+) extrusion was induced in Dunaliella cells by elevation of intracellular Na(+) with Na(+)-specific ionophores. Elevation of intracellular Na(+) was found to enhance the reduction of an extracellular electron acceptor ferricyanide (FeCN). The quinone analogs NQNO and dicumarol inhibited FeCN reduction and led to accumulation of Na(+) by inhibition of Na(+) extrusion. These inhibitors also diminished the plasma membrane potential in Dunaliella. Anaerobic conditions elevated, whereas FeCN partially decreased intracellular Na(+) content. Cellular NAD(P)H level decreased upon enhancement of plasma membrane electron transport. These results are consistent with the operation of an electrogenic NAD(P)H-driven redox system coupled to Na(+) extrusion in Dunaliella plasma membrane. We propose that redox-driven Na(+) extrusion and recycling in Dunaliella evolved as means of adaptation to hypersaline environments.

PMID: 11245805 [PubMed - indexed for MEDLINE]

Synthetic abilities of Euglena chloroplasts in darkness.

Gomez-Silva B, Schiff JA.

Protein synthesis, normally a light-dependent process in isolated mature chloroplasts of Euglena gracilis var. bacillaris will take place in darkness if ATP and Mg2+ (ATP/Mg) are supplied. Either 5 or 10 mM ATP plus 15 mM MgCl2 are optimal and rates equal to those in the light can be obtained. Since ATP and Mg2+ are not stoichiometrically related, and since the optimal Mg2+ concentration is similar to that which stabilizes chloroplast ribosomes in vitro, it is suggested that the chloroplast is freely permeable to Mg2+ under these conditions. Protein synthesis under these conditions is not inhibited appreciably by DCMU, FCCP, cycloheximide, or by the addition of ribonuclease, but is highly sensitive to chloramphenicol. Carbon dioxide fixation is also a light-dependent process in isolated mature chloroplasts from Euglena, but addition of ATP (5 mM) and fructose bisphosphate (5 mM) plus aldolase (1.0 unit/ml) (fructose-1,6-bisphosphate/aldolase) yields CO2 fixation rates in darkness that are 43% of those normally obtained in the light. Mg2+ higher than 1.0 mM (e.g., 16 mM) is somewhat inhibitory. Chlorophyll synthesis from 5-aminolevulinate in 36 h developing chloroplasts from Euglena is also light-dependent, but addition of ATP/Mg and fructose-1,6-bis-phosphate/aldolase in darkness brings about the accumulation of a compound having the same RF on chromatography as protochlorophyllide from Barley; a subsequent brief illumination of the chloroplasts converts this compound to a compound with the RF of chlorophyll. Thus Euglena chloroplasts supplied with appropriate additions can carry out protein synthesis, carbon dioxide fixation and most of chlorophyll synthesis in darkness. This versatility is appropriate in photosynthetic organelles isolated from photo-organotrophic cells.

PMID: 3925991 [PubMed - indexed for MEDLINE]

Photosensory transduction in the flagellated alga, Euglena gracilis. II. Evidence that blue light effects alteration in Na+/K+ permeability of the photoreceptor membrane.

Doughty MJ, Grieser R, Diehn B.

1. The blue light-induced cell tumbling behavior (the step-down photophobic response) and the accumulation of cells into a blue light trap (photoaccumulation) were investigated in Euglena. Dose response plots for these phenomena which we collectively term 'photobehavior' show both threshold and saturation characteristics. 2. NaCl effects apparent elevation in the photosensitivity of the cell as evidenced by alteration of the dose response plot character and lowering of the light intensity saturation level. 3. NaCl and ouabain enhance the duration of the photophobic responses and the rate of photoaccumulation. KCl and NH4Cl have lesser or inhibitory effects. 4. Choline chloride reduces the duration of the photophobic responses and the rate of photoaccumulation. 5. KCl reduces the enhancement of photobehavior induced by NaCl and at constant chloride concentration, photobehavior is unaffected by the relative KCl and NaCl concentrations. 6. Antagonists of voltage-dependent, monovalent cation fluxes in membranes (tetrodotoxin, procaine, tetraethylammonium, 4-aminopyridine) do not alter photobehavior. 7. The results suggest a role for a photoreceptor membrane-located transport system for Na+/K+ as a key step in control of the intraflagellar free Ca/+ levels that determine the photobehavior mediated by flagellar reorientation.

PMID: 6251881 [PubMed - indexed for MEDLINE]

[Accumulation of Tl+ ions in cells of the Black Sea alga Ulva rigida]

[Article in Russian]

Skul'skii IA, Glazunov VV, Zesenko AIa, Liubimov AA.

PMID: 5086083 [PubMed - indexed for MEDLINE]

Transport of amino acids and calcium in the fungus, Phytophthora infestans

Sysuev VA, Kholodenko VP, Okorokov LA.

Amino acid transport in the cells of calcium-dependent fungus Phytophthora infestans has been largely studied with respect to phenylalanine. It is defined as an active process in a number of characteristics. The reasons for that are as follows: 1) accumulation of amino acids is inhibited by carbodiimide and ruthenium red, which suggests the participation of an intermediate; 2) the transport is energy-dependent, since it is inhibited by potassium cyanide, sodium azide and 2,4-dinitrophenol. Cold-osmotic shock results in the inhibition of the amino acid and glucose transport 20-80 times without inhibiting calcium transport. The data obtained suggest that the transport systems of amino acids and calcium are probably not interrelated.

PMID: 889970 [PubMed - indexed for MEDLINE]

Accumulation and transfer of copper by Oocystis pusilla.

Chang C, Sibley TH.

School of Fisheries, University of Washington, Seattle 98195.

PMID: 8490274 [PubMed - indexed for MEDLINE]

Toxicity and accumulation of copper and cadmium in the alga Scenedesmus obliquus LH.

Drbal K, Veber K, Zahradnik J.

PMID: 4016298 [PubMed - indexed for MEDLINE]

Mobilization and accumulation of sediment bound heavy metals by algae.

Laube V, Ramamoorthy S, Kushner DJ.

PMID: 111733 [PubMed - indexed for MEDLINE]

Ionic strength effects in biosorption of metals by marine algae.

Schiewer S, Wong MH.

Department of Biology, Institute for Natural Resources and Waste Management, Hong Kong Baptist University, Kowloon Tong, Hong Kong SAR, People's Republic of China.

Biosorption, the passive accumulation of metals by biomass, can be used as a cost-effective process for the treatment of metal polluted industrial effluents. The green alga Ulva fascia and the brown seaweeds Sargassum hemiphyllum, Petalonia fascia, and Colpomenia sinuosa were characterized in terms of their number of binding sites, their charge density and intrinsic proton binding constant (pKa) using pH titrations at different ionic strengths. The determined number of binding sites decreased in the order Petalonia > or = Sargassum > Colpomenia > Ulva. Due to their high number of binding sites Sargassum and Petalonia are most promising for biosorption applications. The decrease of proton binding with increasing ionic strength and pH as well as the increase of Cu and Ni binding with increasing pH and decreasing ionic strength could be described by the Donnan model in conjunction with an ion exchange biosorption isotherm.

PMID: 10819211 [PubMed - indexed for MEDLINE]

Response to heavy metals in organisms-I. Excretion and accumulation of physiological and non physiological metals in Euglena gracilis.

Albergoni V, Piccinni E, Coppellotti O.

PMID: 6108179 [PubMed - indexed for MEDLINE]

Biosorption of heavy metals by marine algae.

Hamdy AA.

Microbial and Natural Products Chemistry Department, National Research Center, Dokki, Cairo, Egypt.

The ability of four different algae (three brown and one red) that have not been previously studied to adsorb Cr(3+), Co(2+), Ni(2+), Cu(2+), and Cd(2+) ions was investigated. The metal uptake was dependent on the type of biosorbent, with different accumulation affinities towards the tested elements. The HCl-treated biomass decreased the metal biosorptive capacity particularly in the case of Cr(3) adsorption with Laurencia obtusa. The extent of uptake of the different metals with the tested algae was assessed under different conditions such as pH, time of algal residence in solution with the metal, and concentration of algal biomass. The rate of uptake of the different metals was very fast in the first 2 h; thereafter the increase in metal uptake was insignificant. The amount of the metal uptake (5-15 mg range) increased steeply by increasing the weight of the biomass. An exception was L. obtusa, where a parallel increase of the uptake of different metals was observed on increasing the algal mass from 5 to 50 mg.

PMID: 10977888 [PubMed - indexed for MEDLINE]

[Preferential accumulation of alanine and pyruvate kinase activity in Chlorella cells during ammonium assimilation]

[Article in Russian]

Shatilov VP, Kasparova MA, Kretovich VL.

PMID: 4434840 [PubMed - indexed for MEDLINE]

[Difference in coefficients of accumulation of Sr 90 from radioactive fallout and natural Sr in Black Sea organisms]

[Article in Russian]

Sokolova IA, Parchevskii VP.

PMID: 4256385 [PubMed - indexed for MEDLINE]

[Accumulation of natural radioactive elements by azotobacter by the cells of algae and by protozoa]

[Article in Russian]

Krasil'nikov NA, Drobkov AA.

PMID: 5873015 [PubMed - indexed for MEDLINE]

Effects on growth and accumulation of zinc in six seaweed species.

Amado Filho GM, Karez CS, Andrade LR, Yoneshigue-Valentin Y, Pfeiffer WC.

Jardim Botanico do Rio de Janeiro/IBAMA, Brazil. [email protected]

Seaweed species from a coastal area contaminated by heavy metals (Sepetiba Bay) in Rio de Janeiro State (Brazil) presented different levels of Zn concentrations. In some species the levels were 20 times higher than that from a noncontaminated area. The present study was undertaken to investigate the capability of different species to tolerate and accumulate zinc. For this purpose six species, Ulva lactuca, Enteromorpha flexuosa, Padina gymnospora, Sargassum filipendula, Hypnea musciformis, and Spyridia filamentosa, were cultivated under laboratory semistatic conditions in five Zn concentrations in seawater, 10, 20, 100, 1000, and 5000 micrograms.liter-1 for a period of 21 days. All species died at 5000 micrograms.liter-1 of Zn, two species (U. lactuca and E. flexuosa) died at 1000 micrograms.liter-1, and one, H. musciformis, died with 100 micrograms.liter-1. The lowest concentration of Zn that presented growth inhibition in the six species was 20 micrograms.liter-1. The brown alga P. gymnospora presented the highest accumulation level of Zn, and H. musciformis the lowest level. The results of tolerance and accumulation under laboratory conditions, associated with field results, indicate the species of Padina and Sargassum as the best species for monitoring heavy metals in tropical coastal areas, and the potential use of their biomass to remove heavy metals from wastewaters.

PMID: 9378088 [PubMed - indexed for MEDLINE]

Influence of inorganic and triethyl lead on nuclear migration and ultrastructure of Micrasterias.

Meindl U, Roderer G.

Institut fur Pflanzenphysiologie, Universitat Salzburg, Austria.

Developing cells of three strains of the desmidiacean alga Micrasterias were treated with inorganic and triethyl lead and examined by light and electron microscopy. In the concentration range 12 to 30 microM, triethyl lead disturbed normal development of the algae, caused changed dictyosomal ultrastructure, disturbed the formation of the secondary cell wall, and caused accumulation of lipid material. Cell multiplication was strongly inhibited between 5 and 30 microM TriEL in Micrasterias denticulata, showing complete inhibition at 15 microM and above. In addition, nuclear migration of developing Micrasterias cells was selectively disturbed by growth-inhibiting concentrations of TriEL, resulting in unusual positioning of the post-telophase nucleus. Although inorganic lead proved to be much more poisonous to Micrasterias cells than TriEL and caused bursting of the cells even at the low concentration of 3 microM it did not affect nuclear migration. Electron microscopic observations revealed a complete disassembly of the post-telophase system of microtubules which is involved in nuclear migration by TriEL, but no detectable effect on the isthmus system of microtubules which anchors the nucleus in the isthmus. It is concluded that the disturbance of nuclear migration in Micrasterias by TriEL was due to the selective disassembly of the involved microtubule system.

PMID: 2338065 [PubMed - indexed for MEDLINE]

Interest of dynamic tests in acute ecotoxicity assessment in algae.

Jouany JM, Ferard JF, Vasseur P, Gea J, Truhaut R, Rast C.

Sorption of toxics by algae may be important and occurs very early. Thus, a decrease of the experimental toxic concentrations in the medium results in understating toxicity when tests are conducted under static conditions. In this work, two different methods of exposure of algae (Chlorella vulgaris) are studied, the static test and the pseudodynamic test. Acute effects (biological and analytical effects) of inorganic compounds (Cu2+, Cd2+, Pb2+, Cr6+) have been evaluated for 96 hr of exposure; in each case, IC50 is much lower in the dynamic condition than in the static one. The percentage of reduction varies from 55 to 75% after 96 hr. Accumulation of metal by chlorellae is greater when testing by the pseudodynamic way, with Cu2+ and Pb2+. But in the case of Cd2+ and Cr6+, the concentration factors are similar in the two kinds of exposure. These results point out the advantage of the pseudodynamic test, of which the methodology is very easy, for a more realistic assessment of acute ecotoxicity in these organisms.

PMID: 6851933 [PubMed - indexed for MEDLINE]

Accumulation of cadmium in a freshwater food chain experimental model.

Ferard JF, Jouany JM, Truhaut R, Vasseur P.

The study of food chain contamination in nature or in the laboratory requires precise definitions of some terms. A simplified model of a freshwater food chain has been elaborated to try to point out hazards related to the presence of cadmium in the aquatic environment. Three different species belonging to various trophic levels, but to the same aquatic systems were used. The required biological and analytical criteria are described. The time course of the experiment was 34 days starting with a 10-day contamination of the first trophic level (algae). The algae were then separated, washed with fresh medium, and given to the second trophic level (daphnids) to eat for 20 days. The third trophic level (fish) was then introduced for 4 days as a scavenger. The methodology was designed to determine the accumulation of cadmium by daphnids and then fish from the algal source. The results show a high direct bioaccumulation of cadmium in algae. The indirect bioaccumulation of daphnids was of the same order of magnitude, but for fish it was smaller. Nevertheless the cadmium transfer from daphnids to fish was obvious.

PMID: 6851925 [PubMed - indexed for MEDLINE]

Monthly deposition of cadmium in rural and industrial areas of Germany (Bayern, Pfalz, Ruhr district) and its influences upon an agricultural model system.

Runkel KH, Payer HD.

Monthly depositions of cadmium were collected by a modified Bergerhoff method and measured by AAS during a 3-year period in rural areas of the Pfalz and in an industrial area of the Ruhr district. Another one year period included measurements in rural areas of southern Bavaria and on a Dutch island. The log-normally distributed deposition rates of cadmium at the rural areas in southern Germany amounted to only 20% of those of the industrial district. The depositions on the Dutch island were twice as high as the depositions on the rural areas of southern Germany. The monthly cadmium deposition rates show only little periodical fluctuation during the year and scatter around more or less constant median values of 25 and 120 micrograms . m-2 . month-1 at the rural and industrial areas, respectively. When open air mass cultures of algae were taken as an agricultural model, the organisms, depending on their growth rate, accumulated 0.4-4.0 ppm of cadmium (dry matter based). The course of the cadmium accumulation reflects the deposition rate of the area where the algae were grown. No growth depression of the algae due to cadmium can be observed under the given deposition rates.

PMID: 6303745 [PubMed - indexed for MEDLINE]

Observations with Thalassiosira rotula (Meunier) on the toxicity and accumulation of cadmium and nickel.

Dongmann G, Nurnberg HW.

Cadmium and nickel toxicity thresholds based on generation time, maximum cell density, and chain length as toxicity indicators were evaluated from batch cultures of the marine diatom Thalassiosira rotula in nutrient-enriched seawater as substrate. Nickel toxicity is about an order of magnitude or more higher than cadmium toxicity. The toxicity thresholds decrease with increasing illumination and are not significantly affected by 10 mumol/liter EDTA. From the metal accumulation determined by voltammetry average maximum uptakes of 90 micrograms Ni/g DW and 600 micrograms Cd/g DW were determined.

PMID: 7169045 [PubMed - indexed for MEDLINE]

Toxicity and accumulation studies of cadmium (Cd2+) with freshwater organisms of different trophic levels.

Canton JH, Slooff W.

PMID: 7067648 [PubMed - indexed for MEDLINE]

Comparative studies on trace metal levels in marine biota. III. Typical levels and accumulation of toxic trace metals in muscle tissue and organs of marine organisms from different European seas.

Stoeppler M, Nurnberg HW.

PMID: 535554 [PubMed - indexed for MEDLINE]

The Crd1 gene encodes a putative di-iron enzyme required for photosystem I accumulation in copper deficiency and hypoxia in Chlamydomonas reinhardtii.

Moseley J, Quinn J, Eriksson M, Merchant S.

Department of Chemistry and Biochemistry and Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095-1569, USA.

Chlamydomonas reinhardtii adapts to copper deficiency by degrading apoplastocyanin and inducing Cyc6 and Cpx1 encoding cytochrome c(6) and coproporphyrinogen oxidase, respectively. To identify other components in this pathway, colonies resulting from insertional mutagenesis were screened for copper- conditional phenotypes. Twelve crd (copper response defect) strains were identified. In copper-deficient conditions, the crd strains fail to accumulate photosystem I and light-harvesting complex I, and they contain reduced amounts of light-harvesting complex II. Cyc6, Cpx1 expression and plastocyanin accumulation remain copper responsive. The crd phenotype is rescued by a similar amount of copper as is required for repression of Cyc6 and Cpx1 and for maintenance of plastocyanin at its usual stoichiometry, suggesting that the affected gene is a target of the same signal transduction pathway. The crd strains represent alleles at a single locus, CRD1, which encodes a 47 kDa, hydrophilic protein with a consensus carboxylate-bridged di-iron binding site. Crd1 homologs are present in the genomes of photosynthetic organisms. In Chlamydomonas, Crd1 expression is activated in copper- or oxygen-deficient cells, and Crd1 function is required for adaptation to these conditions.

PMID: 10811605 [PubMed - indexed for MEDLINE]

Coordinate expression of coproporphyrinogen oxidase and cytochrome c6 in the green alga Chlamydomonas reinhardtii in response to changes in copper availability.

Hill KL, Merchant S.

Department of Chemistry and Biochemistry, University of California at Los Angeles 90024-1569.

To maintain photosynthetic competence under copper-deficient conditions, the green alga Chlamydomonas reinhardtii substitutes a heme protein (cytochrome c6) for an otherwise essential copper protein, viz. plastocyanin. Here, we report that the gene encoding coproporphyrinogen oxidase, an enzyme in the heme biosynthetic pathway, is coordinately expressed with cytochrome c6 in response to changes in copper availability. We have purified coproporphyrinogen oxidase from copper-deficient C.reinhardtii cells, and have cloned a cDNA fragment which encodes it. Northern hybridization analysis confirmed that the protein is nuclear-encoded and that, like cytochrome c6, its expression is regulated by copper at the level of mRNA accumulation. The copper-responsive expression of coproporphyrinogen oxidase parallels cytochrome c6 expression exactly. Specifically, the copper-sensing range and metal selectivity of the regulatory components, as well as the time course of the responses, are identical. Hence, we propose that the expression of these two proteins is controlled by the same metalloregulatory mechanism. Our findings represent a novel metalloregulatory response in which the synthesis of one redox cofactor (heme) is controlled by the availability of another (Cu).

PMID: 7889936 [PubMed - indexed for MEDLINE]

Erratum in:

EMBO J 1991 Aug;10(8):2320

Dynamic interplay between two copper-titrating components in the transcriptional regulation of cyt c6.

Merchant S, Hill K, Howe G.

Department of Chemistry and Biochemistry, University of California, Los Angeles 90024.

The algal plastidic cytochrome c (cyt c6) is a biochemical equivalent of the copper-containing protein plastocyanin in photosynthetic electron transfer. But generally, cyt c6 accumulates and functions only under conditions (e.g. Cu-deficiency) where holoplastocyanin cannot be synthesized. In studying the regulation of Chlamydomonas reinhardtii cyt c6 expression by Cu we have determined that repression of cyt c6 accumulation occurs at the transcriptional level, and specifically in response to Cu as the metal ion regulator. Complete and sustained repression of cyt c6 transcription requires approximately 9 x 10(6) Cu ions in the medium/cell. Based on the estimated plastocyanin content of algal cells (8 x 10(6) molecules/cell) and the observation that lower ratios of Cu per cell result in only transient repression of cyt c6 transcription, we propose that Cu-dependent transcriptional repression of the gene encoding cyt c6 requires a Cu-binding factor which is titrated by Cu only after the alternate electron transfer catalyst, plastocyanin, has accumulated to the stoichiometry required for photosynthesis. The precise and highly metal-specific, autoregulatory control of cyt c6 levels--directly by Cu, and indirectly by holoplastocyanin--is in keeping with the functional role of cyt c6 as an alternate, although perhaps less preferred, electron transfer catalyst.

PMID: 1863287 [PubMed - indexed for MEDLINE]

Trace metal concentrations in marine macroalgae from different biotopes in the Aegean Sea.

Sawidis T, Brown MT, Zachariadis G, Sratis I.

Department of Botany, University of Thessaloniki, Greece.

The commonest species of red, brown, and green macroalgae were sampled from a range of biotopes in the Aegean Sea and analysed for five different trace metals. Significant differences in metal concentrations were found among different seaweed species from the same biotope. The concentrations of metals in the various seaweed species may reflect their morphology, with those having a larger surface area having a greater internal content. Different species of seaweed have different affinities for different heavy metals. This may reflect competition between metals for binding or uptake sites in the seaweed. Comparing metal concentrations in algae among the studied sampling stations clearly indicates that the degree of accumulation depends not only on human activities but also on the geology of the specific area. While seaweed can be used successfully to assess the levels of heavy metals in the marine environment, not all elevated concentrations of heavy metals necessarily reflect increased levels of pollution. Indeed, the high concentrations of certain metals, e.g., Ni, found in our seaweed samples reflected the metaliferrous nature of the rock. It is therefore important to take account of a region's geology before attempting to interpret the data.

PMID: 11488389 [PubMed - indexed for MEDLINE]

Trace metals in seagrass, algae and molluscs from an uncontaminated area in the Mediterranean.

Campanella L, Conti ME, Cubadda F, Sucapane C.

Dipartimento di Chimica, Universita di Roma La Sapienza, P.le A. Moro 5-00185, Rome, Italy. [email protected]

The concentrations of Cd, Cr, Cu, Pb and Zn were measured in specimens of four marine organisms--the seagrass Posidonia oceanica (L.) Delile, the brown algae Padina pavonica (L.) Thivy, and the two gastropod molluscs Monodonta turbinata Born and Patella caerulea L.--selected as possible cosmopolitan biomonitors of trace metals in the Mediterranean area. The organisms were collected at five coastal sites in Favignana Island (Sicily, Italy), an area virtually uninfluenced by anthropogenic activities. In order to gain a more complete picture of both the environmental conditions of the experimental area and the bioaccumulation patterns of the selected organisms, soluble and total metal concentrations were determined in coastal water samples collected at the same stations. The picture of bioavailable metal loads in the different sites of the selected area provided by the four species was rather univocal. An overall trend of increased metal concentrations at the station in which the local harbour is located was clear. On the other hand, the metal concentrations recorded at the 'clean' stations generally fall in the range of the lowest values available in the literature and may be considered as useful background levels to which to refer for intraspecific comparison within the Mediterranean area. Implications in biomonitoring of the observed accumulation patterns, especially in the different tissues of Posidonia oceanica, are discussed.

PMID: 11202705 [PubMed - indexed for MEDLINE]

Effects of development time, biomass and ferromanganese oxides on nickel sorption by stream periphyton.

Gray BR, Hill WR, Stewart AJ.

Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6351, USA. [email protected]

Procedurally defined periphyton frequently includes substantial quantities of hydrous iron (Fe) and manganese (Mn) oxides. As these oxides are strong sorbers of heavy metals, their presence may complicate estimation of metal bioaccumulation by periphyton. We examined the relationship between nickel (Ni) sorption and the development time, biomass, and Fe and Mn oxide content of stream periphyton. Development time, the time during which periphyton accrued on submerged tile substrata, was used to provide variation in biomass, Fe and Mn levels. Stream periphyton from four development times was exposed to Ni for 2 h in the laboratory, and then ashed. Development time was significantly associated with ash-free dry mass (AFDM), Fe and Mn levels (ANOVA, P < or = 0.003). Ni extracted by a mild reductant (hydroxylamine hydrochloride) was significantly associated with development time, and with AFDM, Fe and Mn levels (linear models, P < or = 0.0002). A subsequent acid digestion yielded similar associations with the same variables (linear models, P < or = 0.0001). For both extractions, AFDM was significantly and positively correlated with Fe (r = 0.68 and 0.89) and with Mn (r = 0.77 and 0.93) (Spearman rank, P < or = 0.005). These data demonstrate the importance of periphyton development time in influencing both metal sorption and levels of biomass and ferromanganese oxides. The data also suggest that metal contaminant levels in periphyton should not be attributed automatically to biotic sorption. Periphyton metal-accumulation studies conducted where ferromanganese oxide concentrations are elevated should address the potential metal-sorbing roles of Fe and Mn oxides within the periphyton matrix.

PMID: 11202655 [PubMed - indexed for MEDLINE]

Effects of major nutrient additions on metal uptake in phytoplankton.

Wang WX, Dei RC.

Department of Biology, Hong Kong University of Science and Technology (HKUST), Clear Water Bay, Kowloon, Hong Kong, People's Republic of China. [email protected]

We examined the influences of major nutrients (N, P, Si) on the accumulation of three trace metals [Cd, Se(IV), and Zn] in four species of marine phytoplankton (diatom, green alga, dinoflagellate, prasinophyte). Relative metal uptake was quantified by the kinetic measurements of metal concentration factor over a short exposure period. Our study demonstrated that nutrient addition significantly influenced the metal uptake rate and the cell growth rate in all four phytoplankton species. An increase in ambient N concentration considerably enhanced metal uptake by the cells. The dry weight concentration factor increased by 2.4-14.9 times for Cd, 1.1-4.0 times for Se, and 1.1-5.4 times for Zn in all four phytoplankton species with an addition of 176.4 microM N. The effects of P or Si addition on metal uptake and cell growth were less pronounced than the effects of N addition. Under most circumstances the rate of metal uptake increased exponentially with increasing cell growth rate constant. Only Se(IV) uptake in the diatom Phaeodactylum tricornutum was not correlated with cell growth rate. Se(IV) was not accumulated by the green algae Chlorella autotrophica at a high P concentration (7.2 microM), but appreciable accumulation was documented in cells inoculated without P addition. Our study therefore demonstrated that nutrient enrichments in many coastal waters can considerably affect trace metal uptake in phytoplankton and presumably metal trophic transfer in marine food chains.

PMID: 11202726 [PubMed - indexed for MEDLINE]

Erratum in:

Environ Sci Technol 2001 Oct 1;35(19):4000

Thiosulfate enhances silver uptake by a green alga: role of anion transporters in metal uptake.

Fortin C, Campbell PG.

INRS-Eau, Universite du Quebec, C.P. 7500, Sainte-Foy, Quebec, Canada, G1V 4C7.

Short-term (< 1 h) silver uptake by the green alga Chlamydomonas reinhardtii was measured in the laboratory in defined inorganic media in the presence or absence of ligands (chloride and thiosulfate). In contradiction to the free-ion model of metal uptake, silver accumulation by the alga proved to be sensitive to the choice of ligand used to buffer the free silver concentration. For a low fixed free Ag+ concentration of 10 nM, silver uptake in the presence of thiosulfate (0.11 microM) was 2x greater than in the presence of chloride (4 mM). When sulfate was removed from the exposure medium (i.e., 81 microM-->0 microM), silver uptake in the presence of thiosulfate was even more markedly enhanced (more than 4x greater than in the presence of chloride). Varying the sulfate concentration in the exposure medium only affected silver uptake if thiosulfate was present. We conclude that silver-thiosulfate complexes are transported across the plasma membrane via sulfate/thiosulfate transport systems and that sulfate acts as a competitive inhibitor of this uptake mechanism.

PMID: 11414021 [PubMed - indexed for MEDLINE]

Influence of N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid pH buffer on the biological response of marine algae.

Vasconcelos MT, Leal MF.

LAQUIPAI, Chemistry Department, Faculty of Science, University of Porto, Portugal. [email protected]

The N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES) is extensively used as pH buffer in culture media for testing chemicals. However, this study demonstrates that 0.01 M HEPES significantly reduces the rate of Cu, Pb, and Cd binding to Porphyra spp. and Enteromorpha spp. marine macroalgae. The HEPES also decreased the accumulation of Cu, Pb, and Cd but not Hg by these macroalgae. Both the extracellular adsorption and the intracellular uptake of the metals were influenced by HEPES to a similar extent. The HEPES also promoted the release of exudates by the algae, and these exudates form very stable complexes with Cu (and probably with other trace metal ions). The HEPES interference varied with the nature of the metal, the macroalga, and the season. The presence of 0.01 M HEPES in seawater cultures of the Emiliania huxleyi (a microalga) also interfered with E. huxleyi growth, liberation of Cu-complexing organic ligands, and Cu uptake. The HEPES, which displays surface activity, may facilitate the binding of metals to the algae for an initial exposure period. The metal taken up appears to stimulate the liberation of exudates that subsequently control the bioavailability of the metals and therefore metal uptake. Because HEPES can control the uptake of trace metals by algae and the production of organic ligands, the results obtained in cultures containing the HEPES pH buffer can be influenced by this component of the media.

PMID: 11837230 [PubMed - indexed for MEDLINE]

Relationship between feeding-induced ventilatory activity and bioaccumulation of dissolved and algal-bound cadmium in the Asiatic clam Corbicula fluminea.

Tran D, Boudou A, Massabuau JC.

UMR 5805, Laboratoire d'Ecophysiologie et Ecotoxicologie des Systemes Aquatiques, Universite Bordeaux I and CNRS, Arcachon, France.

The influence of feeding-induced ventilatory adaptation on cadmium accumulation patterns was analyzed in quiescent Asiatic clam Corbicula fluminea studied in steady-state conditions at 15 degrees C and 25 degrees C and in air-equilibrated water. Ventilatory activity, algae inflow rate, amounts of inspired dissolved and algae-bound Cd, and whole-body and tissue-specific metal concentrations were studied during a 15-d exposure period at a low dissolved cadmium concentration of 2 microg/L and various algal concentrations of Scenedesmus subspicatus. Great care was taken not to externally stimulate animals. Four main results were obtained as regard to regulation of ventilatory activity and metal accumulation rate. First, at 25 degrees C, feeding purposes strongly stimulated ventilatory activity, while at 15 degrees C, it was independent of it except at 1 to 2 x 10(5) algae/ml. Second, Cd accumulation rate increased at higher temperature. Third, accumulation rate exhibited a positive correlation with the ventilatory flow rate. Fourth, no correlation was observed with the quantity of ventilated algae-bound Cd but, rather, with the quantity of ventilated dissolved Cd. It is concluded that the physiology of the animals can be fundamental in affecting metal accumulation process.

PMID: 11833801 [PubMed - indexed for MEDLINE]

Possible control of transcript levels by chlorophyll precursors in Chlamydomonas.

Johanningmeier U.

Ruhr-Universitat Bochum, Lehrstuhl Biochemie der Pflanzen, Federal Republic of Germany.

Steady-state mRNA levels of the three nuclear genes cab1, rbcS1 and rbcS2 (coding for the light-harvesting chlorophyll-binding protein (LHCP) and the small subunit of ribulose 1,5-bisphosphate carboxylase, respectively) and of the two plastid-encoded genes rbcL and psaA2 (coding for the large subunit of the carboxylase and a member of the P700 chlorophyll a protein, respectively) have been investigated in synchronized Chlamydomonas cells in response to light and inhibitors interfering with chlorophyll synthesis. The accumulation of cab1, rbcS1 and psaA2 transcripts is light-dependent, whereas transcripts from rbcS2 and rbcL genes are present in high amounts in the light and in the dark. Dioxoheptanoic acid, an inhibitor blocking chlorophyll synthesis prior to porphyrin formation, does not affect the accumulation of all five mRNAs. However, inhibition of chlorophyll synthesis by incubating cells with dipyridyl, cycloheximide or nitrogen promotes the accumulation of porphyrin compounds, but specifically prevents the accumulation of light-dependent transcripts. Although functionally unrelated, these inhibitors are known to block an Fe-dependent oxygenase, which is involved in the formation of the isocyclic ring in the chlorophyll molecule. The data are explained as a control by chlorophyll precursors over the accumulation of light-dependent transcripts.

PMID: 3056725 [PubMed - indexed for MEDLINE]

Electrogenicity of the Na+-ATPase from the marine microalga Tetraselmis (Platymonas) viridis and associated H+ countertransport.

Balnokin YV, Popova LG, Andreev IM.

Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, Moscow.

Sodium accumulation by the Na+-ATPase in the plasma membrane (PM) vesicles isolated from the marine alga Tetraselmis (Platymonas) viridis was shown to be accompanied by deltapsi generation across the vesicle membrane (positive inside) and H+ efflux from the vesicle lumen. Na+ accumulation was assayed with 22Na+; deltapsi generation was detected by recording absorption changes of oxonol VI; H+ efflux was monitored as an increase in fluorescence intensity of the pH indicator pyranine loaded into the vesicles. Both ATP-dependent Na+ uptake and H+ ejection were increased by the H+ ionophore carbonyl cyanide m-chlorophenylhydrazone (CICCP) while deltapsi was collapsed. The lipophilic anion tetraphenylboron ion (TPB-) inhibited H+ ejection from the vesicles and abolished deltapsi. Based on the effects of CICCP and TPB- on H+ ejection and deltapsi generation, the conclusion was drawn that H+ countertransport observed during Na+-ATPase operation is a secondary event energized by the electric potential which is generated in the course of Na+ translocation across the vesicle membrane. Increasing Na+ concentrations stimulated H+ efflux and caused the decrease in the deltapsi observed, thus indicating that Na+ is likely a factor controlling H+ permeability of the vesicle membrane.

PMID: 10622734 [PubMed - indexed for MEDLINE]

Interactions of chromium with microorganisms and plants.

Cervantes C, Campos-Garcia J, Devars S, Gutierrez-Corona F, Loza-Tavera H, Torres-Guzman JC, Moreno-Sanchez R.

Instituto de Investigaciones Quimico-Biologicas, Universidad Michoacana, Edificio B-3, Ciudad Universitaris, 58030 Morelia, Michoacan, Mexico. [email protected]

Chromium is a highly toxic non-essential metal for microorganisms and plants. Due to its widespread industrial use, chromium (Cr) has become a serious pollutant in diverse environmental settings. The hexavalent form of the metal, Cr(VI), is considered a more toxic species than the relatively innocuous and less mobile Cr(III) form. The presence of Cr in the environment has selected microbial and plant variants able to tolerate high levels of Cr compounds. The diverse Cr-resistance mechanisms displayed by microorganisms, and probably by plants, include biosorption, diminished accumulation, precipitation, reduction of Cr(VI) to Cr(III), and chromate efflux. Some of these systems have been proposed as potential biotechnological tools for the bioremediation of Cr pollution. In this review we summarize the interactions of bacteria, algae, fungi and plants with Cr and its compounds.

Publication Types:

Review

Review, Academic

PMID: 11348688 [PubMed - indexed for MEDLINE]

Proline alleviates heavy metal stress in Scenedesmus armatus.

el-Enany AE, Issa AA.

Botany Department, Faculty of Science, Assiut University, Assiut, Egypt.

Growth and some metabolic activities of Scenedesmus armatus grown in the presence of different heavy metals (Cd, Mn and Ni) with and without exogenously added proline (Pro) were monitored. The growth of S. armatus cells (cell concentration, pigment and dry mass) was inhibited by all these heavy metals. Addition of Pro to the culture medium minimized the toxic effect of the metals. The growth rate was somewhat higher in Pro-containing cultures and started to decline 1 d later than in cultures containing heavy metals alone. S. armatus cells accumulated the added Pro in response to heavy metals. The accumulation correlated with protein content. Cd was the strongest inducer of Pro accumulation, Mn being the weakest. Cells accumulated nickel more than cadmium and manganese. Heavy metal-treated cells had increased peroxidase and catalase activities.

PMID: 11702408 [PubMed - indexed for MEDLINE]

[Alimentary methods for decreasing the radiation load of the body with cesium and strontium radionuclides]

[Article in Russian]

Shandala NK.

Introduction in ration of fish mass, calcium carbonate, bone meal, algae laminaria reduced level of Sr-90 and Cs-137 accumulation in the population living on territories polluted after Chernobyl accident

PMID: 8163235 [PubMed - indexed for MEDLINE]

Natural radionuclide and plutonium content in Black Sea bottom sediments.

Strezov A, Yordanova I, Pimpl M, Stoilova T.

Institute for Nuclear Research and Nuclear Energy, Sofia, Bulgaria.

The content of uranium, thorium, radium, lead, polonium, and plutonium in bottom sediments and algae from two locations at the Bulgarian Black Sea coast have been determined. Some parent:progeny ratios for evaluation of the geochemical behavior of the nuclides have been estimated as well. The extractable and total uranium and thorium are determined by two separate radiochemical procedures to differentiate the more soluble chemical forms of the elements and to estimate the potential hazard for the biosphere and for humans. No distinct seasonal variation as well as no significant change in total and extractable uranium (also for 226Ra) content is observed. The same is valid for extractable thorium while the total thorium content in the first two seasons is slightly higher. Our data show that 210Po content is accumulated more in the sediments than 210Pb, and the evaluated disequilibria suggest that the two radionuclides belong to more recent sediment layers deposited in the slime samples compared to the silt ones for the different seasons. The obtained values for plutonium are in the lower limits of the data cited in literature, which is quite clear as there are no plutonium discharge facilities at the Bulgarian Black Sea coast. The obtained values for the activity ratio 238Pu:239 + 240Pu are higher for Bjala sediments compared to those of Kaliakra. The ratio values are out of the variation range for the global contamination with weapon tests fallout plutonium which is probably due to Chernobyl accident contribution. The dependence of natural radionuclide content on the sediment type as well as the variation of nuclide accumulation for two types of algae in two sampling locations for five consecutive seasons is evaluated. No serious contamination with natural radionuclides in the algae is observed.

PMID: 7499155 [PubMed - indexed for MEDLINE]

Short-term bioconcentration studies of Np in freshwater biota.

Poston TM, Klopfer DC, Simmons MA.

Pacific Northwest Laboratory, Richland, WA 99352.

Short-term laboratory exposures were conducted to determine the potential accumulation of Np in aquatic organisms. Concentration factors were highest in green algae. Daphnia magna, a filter-feeding crustacean, accumulated Np at levels one order of magnitude greater than the amphipod Gammarus sp., an omnivorous substrate feeder. Accumulation of Np in juvenile rainbow trout (Oncorhynchus mykiss) was highest in carcass (generally greater than 78% of the total body burden) and lowest in fillets. Recommended concentration factors for Np, based on fresh weight, were 300 for green algae, 100 for filter-feeding invertebrates, for nonfilter-feeding invertebrates, 10 for whole fish, and one for fish flesh.

PMID: 2228614 [PubMed - indexed for MEDLINE]

Synopsis of French experimental and in situ research on the terrestrial and marine behavior of Tc.

Masson M, Patti F, Colle C, Roucoux P, Grauby A, Saas A.

Laboratoire de Radioecologie Marine, C.E.A., I.P.S.N., D.E.R.S., S.E.R.E., Cherbourg, France.

Terrestrial environment studies have been essentially concerned with the evolution of soil deposition and soil-plant transfers. Experimentally determined coefficients of distribution in soils are low: 60-80% of Tc remains hydrosoluble during the first months. Technetium emissions resulting from microbiological activity have been quantified. Antagonistic effects on Mo and Tc retention by soils are dependent on their respective concentrations. Four areas of soil-plant transfers have been studied: 1) root absorption kinetics relative to deposition of Tc, 2) interaction of stable Mo (environmental parameter) with the transfer of Tc to plants, 3) interaction of some long-lived radioisotopes (effluent parameters) with the transfer of Tc to plants, and 4) long-term soil-plant transfer and aging of deposited material. Of aquatic systems, only the marine environment has been studied. Under anoxic conditions in the presence of reducing sediments, the distribution coefficients (Kd) were very high (10(3)). Concentration factors (CF) from water to organisms were generally very low (1 to 10); however, CF greater than 1000 have been observed for some biota such as macrophytic brown algae, worms and lobsters. Biochemical analysis showed that Tc was essentially free and partially bonded to proteins. The transfer factors between sediments and species were very low (TF less than 0.5). The biological half-time was determined in some marine organisms that had accumulated Tc from water, food or sediments; the loss is biphasic. Uptake in edible parts was low. The physiochemical form affects the accumulation and loss of Tc. Analyses have quantified 99Tc in marine fauna and biota in the English Channel in relation with releases of the reprocessing plant of La Hague. Brown algae are the best bioindicators for following 99Tc dispersion in marine ecosystems.

Publication Types:

Review

Review, Tutorial

PMID: 2668233 [PubMed - indexed for MEDLINE]

Rapid accumulation of plutonium and polonium on giant brown algae.

Hodge VF, Hoffman FL, Folsom TR.

PMID: 4430628 [PubMed - indexed for MEDLINE]

Factors influencing radiostrontium accumulation in Daphnia.

Porcella DB, Rixford CE, Slater JV.

PMID: 6029684 [PubMed - indexed for MEDLINE]

The syntheses of plastocyanin and cytochrome c-553 are regulated by copper at the pre-translational level in a green alga, Pediastrum boryanum.

Nakamura M, Yamagishi M, Yoshizaki F, Sugimura Y.

Department of Biology, Faculty of Science, Toho University, Chiba.

The green alga Pediastrum boryanum synthesizes alternatively two photosynthetic electron carrier proteins, plastocyanin and cytochrome c-553, depending on the copper concentration of the medium. We studied the levels at which the syntheses of the two proteins are regulated. Plastocyanin and cytochrome c-553 were purified from P. boryanum NIES-301 cells, having apparent molecular weights of 14,600 and about 12,000, respectively. Western blotting with antisera raised against these proteins showed accumulation of (apo)plastocyanin and (apo)cytochrome c-553 in the cells grown with (2 microM) and without added CuSO4, respectively, but no accumulation of the precursor proteins in both cultures. The translatable mRNAs for the two proteins were examined by in vitro translation with total RNA and wheat germ extract followed by immunoprecipitation and SDS-PAGE. The 21-kDa polypeptide (preapoplastocyanin) was detected with anti-plastocyanin serum in copper-sufficient cells; the 23-kDa polypeptide (preapocytochrome c-553) with anti-cytochrome c-553 serum in copper-deficient cells. The translatable mRNA for preapoplastocyanin appeared in 1 h and (apo)plastocyanin in 2-3 h after the addition of 2 microM CuSO4 to the copper-deficient culture. The translatable mRNA for preapocytochrome c-553 disappeared within 4-5 h, while (apo)cytochrome c-553 disappeared more slowly. It is concluded that the syntheses of plastocyanin and cytochrome c-553 are regulated by copper at the pre-translational (i.e., transcriptional or post-transcriptional) level in P. boryanum NIES-301.

PMID: 1314811 [PubMed - indexed for MEDLINE]

Overexpression and characterization of carboxyl-terminal processing protease for precursor D1 protein: regulation of enzyme-substrate interaction by molecular environments.

Yamamoto Y, Inagaki N, Satoh K.

Department of Biology, Faculty of Science, Okayama University, Okayama 700-8530, Japan.

CtpA, which is classified as a novel type of serine protease with a Ser/Lys catalytic dyad, is responsible for the C-terminal processing of precursor D1 protein (pD1) of the photosystem II reaction center, a process that is indispensable for the integration of water-splitting machinery in photosynthesis. In this study, overexpression in Escherichia coli and one-step purification of spinach CtpA were carried out to analyze the characteristics of this new type of protease and to elucidate the molecular interactions in the C-terminal processing of pD1 on the thylakoid membrane. The successful accumulation of functional CtpA in E. coli may argue against the possibility, based on homology to E. coli Tsp, that the enzyme is involved in the degradation of incomplete proteins in chloroplasts, e.g. by utilizing the ssrA-tagging system. Analysis using a synthetic pD1 oligopeptide demonstrated that the enzymatic properties (including substrate recognition) of overexpressed CtpA with an extra sequence of GSHMLE at the N terminus were indistinguishable from those of the native enzyme. CtpA was insensitive to penem, which has been shown to inhibit some Ser/Lys-type proteases, suggesting that the catalytic center of CtpA is quite unique. By using the substrate in different molecular environments (i.e. synthetic pD1 oligopeptide in solution and pD1 in photosystem II-enriched thylakoid membrane), we observed a dramatic difference in the pH profile and affinity for the substrate, suggesting the presence of a specific interaction of CtpA with a factor(s) that modulates the pH dependence of proteolytic action in response to physiological conditions.

PMID: 11099501 [PubMed - indexed for MEDLINE]

A structurally novel transferrin-like protein accumulates in the plasma membrane of the unicellular green alga Dunaliella salina grown in high salinities.

Fisher M, Gokhman I, Pick U, Zamir A.

Department of Biochemistry, Weizmann Institute of Science, Rehovot 76100, Israel.

The alga Dunaliella salina is outstanding is its ability to withstand extremely high salinities. To uncover mechanisms underlying salt tolerance, a search was carried out for salt-induced proteins. The level of a plasma membrane 150-kDa protein, p150, was found to increase with rising external salinity (Sadka, A., Himmelhoch, S., and Zamir, A. (1991) Plant Physiol. 95, 822-831). Based on its cDNA-deduced sequence, p150 belongs to the transferrin family of proteins so far identified only in animals. This, to our best knowledge, is the first demonstration of a transferrin-like protein in a photosynthetic organism. Unlike animal transferrins, p150 contains three, rather than two, internal repeats and a COOH-terminal extension including an acidic amino acid cluster. In intact cells p150 is degraded by Pronase, indicating that the protein is extracellularly exposed. The relationship of p150 to iron uptake is supported by the induction of the protein in iron-deficient media and by its radioactive labeling in cells grown with 59Fe. Accumulation of p150 is transcriptionally regulated. It is proposed that p150 acts in iron uptake other than by receptor-mediated endocytosis and that its induction permits the cells to overcome a possible limitation in iron availability under high salinities.

PMID: 8999829 [PubMed - indexed for MEDLINE]

Degradation of plastocyanin in copper-deficient Chlamydomonas reinhardtii. Evidence for a protease-susceptible conformation of the apoprotein and regulated proteolysis.

Li HH, Merchant S.

Department of Chemistry and Biochemistry, University of California at Los Angeles 90095-1569, USA.

In the green alga Chlamydomonas reinhardtii, the copper-dependent accumulation of plastocyanin is effected via the altered stability of the protein in copper-deficient versus copper-sufficient medium (t1/2) < 20 min versus several hours). To understand the mechanism of plastocyanin degradation in vivo, the purified apoprotein was characterized relative to the holoprotein with respect to conformation and protease susceptibility. Circular dichroism spectroscopy revealed that the apoprotein in solution did not display the characteristic secondary structure displayed by the native or reconstituted holoprotein. The apoprotein was also susceptible to digestion in vitro by chymotrypsin whereas the holoprotein was resistant. High ionic conditions, which stabilize the folded structure of apoplastocyanin, also inhibit its degradation by chymotrypsin. These results suggest that one explanation for plastocyanin degradation in copper-deficient cells in vivo might be the increased susceptibility of the apo form to a lumenal protease. Since apoplastocyanin is a normal biosynthetic intermediate for the formation of holoplastocyanin, the increased susceptibility of apoplastocyanin to proteolysis implies that degradative and biosynthetic activities would compete for the same substrate. However, characterization of an apoplastocyanin-accumulating mutant suggests that a plastocyanin-degrading protease is active only in copper-deficient cells. Thus, apoplastocyanin is rapidly degraded in copper-deficient cells, whereas its major fate in copper-supplemented cells is holoplastocyanin formation.

PMID: 7559514 [PubMed - indexed for MEDLINE]

Two metal-dependent steps in the biosynthesis of Scenedesmus obliques plastocyanin. Differential mRNA accumulation and holoprotein formation.

Li HH, Merchant S.

Department of Chemistry and Biochemistry, UCLA 90024.

The accumulation of the interchangeable electron transfer catalysts plastocyanin and cytochrome c6 (cyt c6) in Scenedesmus obliquus is reciprocally regulated by the amount of copper ions in the medium. In copper-deficient cells, plastocyanin levels are severely reduced, whereas cyt c6 levels are high. Western blot analysis indicates that neither pre-apoplastocyanin nor apoplastocyanin accumulate to significant extents in copper-deficient Scenedesmus cells, and time course studies indicate that upon provision of copper salts to copper-deficient cells, the accumulation of plastocyanin to the levels maintained in copper-sufficient cells takes about 12-24 h. By 1) Northern hybridization analysis of Scenedesmus obliquus mRNA and 2) in vitro translation of polyadenylylated mRNA followed by immunoprecipitation of a 19.2-kilodalton precursor to plastocyanin, we demonstrate that the regulation of plastocyanin synthesis by copper must occur primarily at the level of mRNA accumulation. These results suggest that copper-dependent stimulation of holoplastocyanin accumulation requires de novo synthesis of the pre-apoprotein and contradict the conclusion of Bohner, H., Bohme, H., and Boger, P. (1981) FEBS Lett. 131, 386-388 that high levels of apoplastocyanin and a precursor to plastocyanin accumulate in copper-deficient Scenedesmus cells. We note also that although metal ions other than copper (e.g. silver) insert into Scenedesmus obliquus plastocyanin in vitro, synthesis of holoplastocyanin in vivo is specific for copper versus silver or mercury as it is in Chlamydomonas reinhardtii. Finally, the very different electrophoretic mobility and immunoreactivity of apoplastocyanin compared with holoplastocyanin suggests rather significant differences in structure between the copper-protein and the metal-free protein.

PMID: 1577764 [PubMed - indexed for MEDLINE]

Isolation and structural characterization of the Chlamydomonas reinhardtii gene for cytochrome c6. Analysis of the kinetics and metal specificity of its copper-responsive expression.

Hill KL, Li HH, Singer J, Merchant S.

Department of Chemistry and Biochemistry, UCLA 90024.

We have isolated a 5-kilobase pair fragment of genomic DNA containing the entire coding region for the Chlamydomonas reinhardtii gene encoding the copper-repressible Cyt c6. A region comprising 2.6 kilobase pairs contains the entire transcribed region plus 852 nucleotides upstream of the Cyt c6 transcription start site and 495 nucleotides downstream of the conserved C. reinhardtii polyadenylation signal. Comparison of the genomic sequence with the cDNA sequence (Merchant, S., and Bogorad, L. (1987) J. Biol. Chem. 262, 9062-9067) revealed that the coding region is interrupted by two introns, each of which is flanked by C. reinhardtii consensus intron/exon boundaries. Primer extension and S1 nuclease protection analyses identified the 5' border of the Cyt c6 mRNA at approximately 79 base pairs upstream from the initiator methionine. Analysis of the 5' upstream region reveals no significant similarity to sequences found in upstream regions of other copper-regulated genes. Time-course studies indicate that 1) the mature Cyt c6 mRNA has a half-life of approximately 45-60 min and is completely lost within 4 h, and 2) the primary, unspliced transcript has a half-life of approximately 10 min and is completely lost within 30 min after the addition of copper ions to copper-depleted cells. These results indicate that the response to copper occurs very rapidly upon elevation of extracellular copper levels. Although this gene is unresponsive to silver ions in vivo, in contrast to the yeast copper-responsive CUP1 gene (Furst, P., Hu, S., Hackett, R., and Hamer, D. (1988) Cell 55, 705-717), it does respond to mercury ions, albeit with less sensitivity. Mercury ions cannot, however, substitute for copper in allowing the accumulation of plastocyanin in vivo.

PMID: 1714451 [PubMed - indexed for MEDLINE]

Rapid degradation of apoplastocyanin in Cu(II)-deficient cells of Chlamydomonas reinhardtii.

Merchant S, Bogorad L.

Although plastocyanin is not detected in Cu(II)-deficient cells of Chlamydomonas reinhardtii, accumulation of messenger RNA for pre-apoplastocyanin is independent of the concentration of Cu(II) in the medium (Merchant, S., and Bogorad, L. (1986) Mol. Cell. Biol. 6, 462-469). This work shows that the synthesis, transport, and processing of pre-apoplastocyanin also appear to be unaffected in cells grown in Cu(II)-deficient medium. However, the mature protein, presumably formed after import of the precursor into the chloroplast, is rapidly degraded in Cu(II)-deficient cells. The half-life of the mature protein is estimated to be between 16 and 18 min in cells grown in Cu(II)-deficient medium. In cells grown in medium containing Cu(II), the mature protein is stable. The proteolytic activity thus appears to be specific for apoplastocyanin versus plastocyanin and thereby accounts for the absence of accumulated plastocyanin in Cu(II)-deficient cells. This process may be part of a general mechanism designed to remove chloroplast proteins which cannot be utilized.

PMID: 3023330 [PubMed - indexed for MEDLINE]

Screening of marine microalgae for bioremediation of cadmium-polluted seawater.

Matsunaga T, Takeyama H, Nakao T, Yamazawa A.

Department of Biotechnology, Tokyo University of Agriculture and Technology, Japan. [email protected]

Twenty four strains out of 191 marine microalgal strains exhibited cadmium (Cd) resistance. They were tested for their Cd removal ability in growth media containing 50 microM Cd. Six strains out of 19 green algae and one out of five cyanobacteria removed more than 10% of total Cd from the medium. The marine green alga Chlorella sp. NKG16014 showed the highest removal of Cd 48.7% of total. Cd removal by NKG16014 was further quantitatively evaluated by measuring the amount of cell adsorption and intracellular accumulation. After 12 days incubation, 67% of the removed Cd was accumulated intracellularly and 25% of the Cd removed was adsorbed on the algal cell surface. The maximum Cd adsorption (qmax) was estimated to be 37.0 mg Cd (g dry cells)-1 using the Langmuir sorption model. The Cd removal by freeze-dried NKG16014 cells was also determined. Cd was more quickly adsorbed by dried cells than that by living cells, with a qmax of 91.0 mg Cd (g dry cells)-1.

PMID: 10412204 [PubMed - indexed for MEDLINE]

Deflagellation of Chlamydomonas reinhardtii follows a rapid transitory accumulation of inositol 1,4,5-trisphosphate and requires Ca2+ entry.

Yueh YG, Crain RC.

Department of Molecular and Cell Biology, University of Connecticut, Storrs 06269-3125.

C. reinhardtii sheds its flagella in response to acidification. Previously, we showed correlations between pH shock, deflagellation, and inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] production, but 100% of cells deflagellated by 5 s, which was the earliest that Ins(1,4,5)P3 accumulation could be accurately measured by techniques available to us at that time (Quarmby, L. M., Y. G. Yueh, J. L. Cheshire, L. R. Keller, W. J. Snell, and R. C. Crain. J. Cell Biol. 1992. 116:737-744). To learn about the causal relationship between Ins(1,4,5)P3 accumulation and deflagellation, we extended these studies to early times using a continuous-flow rapid-quench device. Within 1 s of acidification to pH 4.3-4.5, 100% of cells deflagellated. A transient peak of Ins(1,4,5)P3 was observed 250-350 ms after pH shock, preceding deflagellation. Preincubation with 10 microM neomycin, which prevents hydrolysis of phosphatidylinositol 4,5-bisphosphate, inhibited both the transient production of Ins(1,4,5)P3 and the subsequent deflagellation. The nonspecific Ca2+ channel blockers La3+ and Cd2+ prevented flagellar excision induced by mastoparan without inhibiting rapid Ins(1,4,5)P3 production. Likewise, the Ins(1,4,5)P3-gated channel inhibitors ruthenium red and heparin blocked deflagellation in response to mastoparan. These studies were extended to mutants defective in flagellar excision. Fa-1, a mutant defective in flagellar structure, produced Ins(1,4,5)P3 but failed to deflagellate. These results support a model in which acid pH activates a putative cellular receptor leading to G-protein dependent activation of phospholipase C and accumulation of Ins(1,4,5)P3. These events are upstream of Ins(1,4,5)P3-dependent Ca2+ entry from the medium, and of deflagellation.

PMID: 8227146 [PubMed - indexed for MEDLINE]

Role of zinc in cell division of Euglena gracilis.

Falchuk KH, Fawcett DW, Vallee BL.

Euglena gracilis is a suitable model system to investigate the role of zinc in the process of cell division. In zinc-deficient organisms there is a characteristic arrest of cellular proliferation, the DNA content of the cells doubles, whereas RNA and protein contents decrease. The present investigations include the growth characteristics, changes in cellular morphology at various stages in the growth cycle, quantitation of zinc uptake and incorporation of tritium-labelled precursors into RNA by organisms grown in zinc sufficient (Zn+), (Zn2+ content 1 times 10-minus 5 M) or zinc-deficient (Zn minus), (Zn2+ content 1 times 10-7 M) medium. Cell division ceases on depletion of zinc from the medium. There are 20-fold less cells in (Zn minus) medium than in control cultures. The size of (Zn+) cells decreases during log phase due to a reduction in the paramylon content of the cytoplasm. The size of (Zn minus) cells, however, increases, due to an accumulation of paramylon. This results in a 13-fold increment in dry weight compared to control. Other cytoplasmic organelles, including Golgi bodies, mitochondria, etc. are normal. Nuclear morphology also is unchanged. There is a reduction in the rate of incorporation of labelled precursors into RNA by (Zn minus) cells. The DNA content of (Zn minus) E. gracilis, the absence of morphologic evidence to indicate that cell division has followed the doubling of the DNA, and the arrest in proliferation suggests that a critical zinc-dependent step in the cell cycle, localized to G2, is blocked in zinc deficiency.

PMID: 803510 [PubMed - indexed for MEDLINE]

Hygienic importance of increased barium content in some fresh waters.

Havlik B, Hanusova J, Ralkova J.

In surface waters of the mining and processing areas of uranium ore there is an increased content of free and bound barium ions due to the use of barium salts for the treatment of waste and mine waters containing radium. In model experiments with the algae Ankistrodesmus falcatus, Chlorella kessleri and Scenedesmus obliquus, we studied the effect of Ba2+ on the accumulation of 226Ra. It was found that the accumulation of radium by algae is negatively influenced with barium concentrations higher than 1 mg.l-1. The accumulation of barium of organisms of primary production was studied using 133BaCl2. At a barium content in the medium of 4.0, 0.46 and 0.04 mu. l-1, the algae accumulated 30-60% of the added amount of barium during an exposure of 15 days. Biochemical analyses showed that barium is bound to the cellular membrane and to other components of the algal cell that cannot be extracted with water or alcohol.

PMID: 7462608 [PubMed - indexed for MEDLINE]

Caesium accumulation by microorganisms: uptake mechanisms, cation competition, compartmentalization and toxicity.

Avery SV.

School of Pure and Applied Biology, University of Wales College of Cardiff, UK.

The continued release of caesium radioisotopes into the environment has led to a resurgence of interest in microbe-Cs interactions. Caesium exists almost exclusively as the monovalent cation Cs+ in the natural environment. Although Cs+ is a weak Lewis acid that exhibits a low tendency to form complexes with ligands, its chemical similarity to the biologically essential alkali cation K+ facilitates high levels of metabolism-dependent intracellular accumulation. Microbial Cs+ (K+) uptake is generally mediated by monovalent cation transport systems located on the plasma membrane. These differ widely in specificity for alkali cations and consequently microorganisms display large differences in their ability to accumulate Cs+; Cs+ appears to have an equal or greater affinity than K+ for transport in certain microorganisms. Microbial Cs+ accumulation is markedly influenced by the presence of external cations, e.g. K+, Na+, NH4+ and H+, and is generally accompanied by an approximate stoichiometric exchange for intracellular K+. However, stimulation of growth of K(+)-starved microbial cultures by Cs+ is limited and it has been proposed that it is not the presence of Cs+ in cells that is growth inhibitory but rather the resulting loss of K+. Increased microbial tolerance to Cs+ may result from sequestration of Cs+ in vacuoles or changes in the activity and/or specificity of transport systems mediating Cs+ uptake. The precise intracellular target(s) for Cs(+)-induced toxicity has yet to be clearly defined, although certain internal structures, e.g. ribosomes, become unstable in the presence of Cs+ and Cs+ is known to substitute poorly for K+ in the activation of many K(+)-requiring enzymes.

Publication Types:

Review

Review, Tutorial

PMID: 7766213 [PubMed - indexed for MEDLINE]

[Dynamics of accumulation of microelements in Chlorella cells during prolonged cultivation]

[Article in Russian]

Pokrovskaia EI, Meleshko GI, Zhurenko VN, Filatkina LA, Zhukova LB.

PMID: 4431217 [PubMed - indexed for MEDLINE]

Synthesis and stability of phytochelatins induced by cadmium and lead in the marine diatom Phaeodactylum tricornutum.

Morelli E, Scarano G.

Consiglio Nazionale delle Ricerche, Istituto di Biofisica, Pisa, Italy. [email protected]

The synthesis of phytochelatins (PC), intracellular metal-binding polypeptides characterized by a repeating sequence of gamma-glutamic acid- cysteine (gamma-Glu-Cys) pairs, has been studied in laboratory cultures of the marine diatom Phaeodactylum tricornutum exposed to Cd, Pb or Zn. Cd and Pb were able to induce PC of different degree of polymerization. The accumulation of the peptides follows a direct relationship with the metal exposure. No PC induction was observed in Zn-treated cultures, although the intracellular concentration of Zn increased during exposure. Both in short-term (7 h exposure, 10 microM Cd or Pb) and 3-day experiments (metal concentration less than 0.5 microM), the major fraction of total PC gamma-Glu-Cys subunits synthesized was polymerized as PC2 when cells were exposed to Pb, but as PC4 when cells were exposed to Cd. In short-term experiments about 50% of the gamma-Glu-Cys residues of the cellular pool of glutathione was quickly and almost quantitatively converted into PC. Recovery experiments, in which metal-stressed cells are suspended in a metal-free medium, showed a decrease of the PC pool and a concomitant increase of glutathione, suggesting a mechanism of degradation and release of metal-phytochelatin complexes.

PMID: 11695656 [PubMed - indexed for MEDLINE]

Regulation by copper of the expression of plastocyanin and cytochrome c552 in Chlamydomonas reinhardi.

Merchant S, Bogorad L.

Plastocyanin and cytochrome c552 are interchangeable electron carriers in the photosynthetic electron transfer chains of some cyanobacteria and green algae (P. M. Wood, Eur. J. Biochem. 87:9-19, 1978; G. Sandmann et al., Arch. Microbiol. 134:23-27, 1983). Chlamydomonas reinhardi cells respond to the availability of copper in the medium and accordingly accumulate either plastocyanin (if copper is available) or cytochrome c552 (if copper is not available). The response occurs in both heterotrophically and phototrophically grown cells. We have studied the molecular level at which this response occurs. No immunoreactive polypeptide is detectable under conditions where the mature protein is not spectroscopically detectable. Both plastocyanin and cytochrome c552 appear to be translated (in vitro) from polyadenylated mRNA as precursors of higher molecular weight. RNA was isolated from cells grown either under conditions favorable for the accumulation of plastocyanin (medium with Cu2+) or for the accumulation of cytochrome c552 (without Cu2+ added to the medium). Translatable mRNA for preapoplastocyanin was detected in both RNA preparations, although mature plastocyanin was detected in C. reinhardi cells only when copper was added to the culture. Translatable mRNA for preapocytochrome, on the other hand, was detected only in cells grown under conditions where cytochrome c552 accumulates (i.e., in the absence of copper). We conclude that copper-mediated regulation of plastocyanin and cytochrome c552 accumulation is effected at different levels, the former at the level of stable protein and the latter at the level of stable mRNA.

PMID: 3023849 [PubMed - indexed for MEDLINE]

Induction of plant gp91 phox homolog by fungal cell wall, arachidonic acid, and salicylic acid in potato.

Yoshioka H, Sugie K, Park HJ, Maeda H, Tsuda N, Kawakita K, Doke N.

Plant Pathology Laboratory, Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Japan. [email protected]

The oxidative burst has been suggested to be a primary event responsible for triggering the cascade of defense responses in various plant species against infection with avirulent pathogens or pathogen-derived elicitors. The molecular mechanisms of rapid production of active oxygen species (AOS), however, are not well known. We isolated homologs of gp91 phox, a plasma membrane protein of the neutrophil NADPH oxidase, from a potato cDNA library. Molecular cloning of the cDNA showed that there are two isogenes, designated StrbohA and StrbohB, respectively. The RNA gel blot analyses showed that StrbohA was constitutively expressed at a low level, whereas StrbohB was induced by hyphal wall components (HWC elicitor) from Phytophthora infestans in potato tubers. Treatment of potato tubers with HWC elicitor caused a rapid but weak transient accumulation of H2O2 (phase I), followed by a massive oxidative burst 6 to 9 h after treatment (phase II). Diphenylene iodonium (DPI), an inhibitor of the neutrophil NADPH oxidase, blocked both bursts, whereas pretreatment of the protein synthesis inhibitor cycloheximide with the tuber abolished only the second burst. These results suggest that the expression of StrbohA and StrbohB contributes to phase I and II bursts, respectively. The same is true for arachidonic acid, a lipid component of P. infestans-stimulated biphasic oxidative burst, whereas an endogenous signaling molecule, salicylic acid, only induced a weak phase II burst. Both molecules induced the StrbohB expression, which is in agreement with the second burst. To characterize the signal transduction pathway leading to the oxidative burst, we examined the role of protein phosphorylation in HWC-stimulated StrbohB gene expression. K252a and staurosporine, two protein kinase inhibitors, blocked the transcript accumulation. Two inhibitors of extracellular Ca2+ movement, however, did not abolish the transcript accumulation of StrbohB, suggesting that certain calcium-independent protein kinases are involved in the process of StrbohB gene expression. Additionally, we examined a causal relationship between the oxidative burst and expression of defense genes induced by the HWC elicitor. The transcript accumulation of genes related to sesquiterpenoid phytoalexin synthesis (lubimin and rishitin) and phenylpropanoid pathway was inhibited slightly by the DPI treatment, suggesting that the oxidative burst is not essential to activate these genes. Interestingly, the concomitant presence of DPI with the elicitor resulted in an increase in lubimin accumulation and a decrease in rishitin accumulation. Because it is known that lubimin is metabolized into rishitin via oxylubimin, we propose that AOS mediates the synthesis of rishitin from lubimin.

PMID: 11386368 [PubMed - indexed for MEDLINE]

[Effect of zooxanthellatoxin-A, an unique marine product, on arachidonic acid cascade in rabbit platelets]

[Article in Japanese]

Nakahata N, Rho M, Ohizumi Y.

Department of Pharmaceutical Molecular Biology, Faculty of Pharmaceutical Sciences, Tohoku University, Sendai, Japan.

Zooxanthellatoxin-A (ZT-A), a bioactive substance isolated from a symbiotic marine alga Symbiodinium sp., caused rabbit platelet aggregation. ZT-A-induced aggregation was dependent on the presence of external Ca2+, and was inhibited by several Ca2+ channel antagonists except L-type one. Furthermore, ZT-A-induced aggregation was attenuated by genistein, indomethacin and SQ29548, indicating that tyrosine phosphorylation and thromboxane A2 (TXA2) are involved in the aggregation. In fact, ZT-A released arachidonic acid and accumulated TXB2, a stable metabolite of TXA2, which was inhibited by genistein. ZT-A caused phosphorylation and activation of mitogenactivated protein kinase (MAPK), which was known to activate cytosolic phospholipase A2 (cPLA2). ZT-A caused the activation of phospholipase C (PLC)-gamma 2, resulting in an accumulation of diacylglycerol that activates protein kinase C (PKC). The MAPK activation was inhibited by genistein and staurousporine. ZT-A is not a Ca(2+)-lonophore, since its different responsibility from ionomycin to external Ca2+, indomethacin and 12-HETE, a platelet lipoxygenase product. These results suggest that ZT-A stimulates PKC a tyrosine kinase with influxed Ca2+, resulting in the activation PLC-gamma 2 that stimulates via diacylglycerol. Then, MAPK is activated by a PKC pathway, then cPLA2 is activated by MAPK. The released arachidonic acid is rapidly converted to TXA2 which causes platelet aggregation.

PMID: 9503430 [PubMed - indexed for MEDLINE]

Induction of two prenyltransferases for the accumulation of coumarin phytoalexins in elicitor-treated Ammi majus cell suspension cultures.

Hamerski D, Schmitt D, Matern U.

Department of Plant Biochemistry, University of Freiburg, F.R.G.

Two dimethylallyl diphosphate:umbelliferone dimethylallyltransferase (prenyltransferase) activities, catalysing the 6-prenylation and the 7-O-prenylation, respectively, of umbelliferone in the course of phytoalexin synthesis, increased in Ammi majus cell suspension cultures in response to elicitor treatment. Both enzyme activities were dependent on Mg2+ or Mn2+ with significant preference for Mg2+ in the 6-prenylation reaction. Whereas dark-grown cells did not contain these activities, both prenyltransferase activities were induced rapidly by the addition of elicitor reaching a first maximum after 10-14 hr and a second maximum beyond 30 hr. Other coumarin specific, elicitor-induced enzyme activities of A. majus cells, in contrast, showed only one maximum of activity within the 50 hr experimental period, while the pattern of induction of phenylalanine ammonia-lyase activity resembled that of the prenyltransferases with maxima at ca 8 hr and 20-30 hr. Preliminary data suggest that the apparent biphasic induction of these enzyme activities is due to post-translational enzyme modifications.

PMID: 1366425 [PubMed - indexed for MEDLINE]

Two copper-responsive elements associated with the Chlamydomonas Cyc6 gene function as targets for transcriptional activators.

Quinn JM, Merchant S.

Department of Chemistry and Biochemistry, University of California at Los Angeles 90095-1569, USA.

In Chlamydomonas reinhardtii, cytochrome c6 (cyt c6) is synthesized only under conditions of copper deficiency when plastocyanin cannot be synthesized. In previous work, the copper-responsive regulation of cyt c6 synthesis was demonstrated to occur by control of transcription, with no contribution from post-transcriptional processes. To understand the mechanism underlying its regulation, the genomic DNA encoding cyt c6 (Cyc6) was analyzed for the presence of copper-responsive elements. Sequences lying between positions -127 and -7 with respect to the start site of transcription were found to be sufficient to confer copper-responsive expression on either a promoterless or a minimal beta-tubulin promoter-driven (arylsulfatase-encoding) reporter gene. Analysis of this 120-bp fragment indicated that copper-responsive elements lie in two distinct regions (between -110 to -56 and -127 to -109). ATG fusions between copper-insensitive promoters and the coding plus 3' untranslated region of the Cyc6 gene resulted in the accumulation of cyt c6 in copper-supplemented medium; this confirms earlier studies indicating a lack of post-transcriptional control in this copper-responsive pathway. In the context of a constitutive promoter (derived from the beta-tubulin gene), each region was found to function as an activator of transcription in copper-deficient cells, and the metal specificity of the response of reporter genes containing either one or both regions was identical to that of the endogenous Cyc6 gene. The copper-responsive synthesis of cyt c6 is thus attributed to these two 5' upstream sequences.

PMID: 7780310 [PubMed - indexed for MEDLINE]

Phytophthora parasitica elicitor-induced reactions in cells of Petroselinum crispum.

Fellbrich G, Blume B, Brunner F, Hirt H, Kroj T, Ligterink W, Romanski A, Nurnberger T.

Institute of Plant Biochemistry, Department of Stress and Developmental Biology, Halle/Saale, Germany.

Cultured parsley (Petroselinum crispum) cells respond to treatment with elicitors derived from different species of the genus Phytophthora with transcript accumulation of defense-associated genes and the production of furanocoumarin phytoalexins. Pep-25, an oligopeptide fragment of a Phytophthora sojae 42-kDa cell wall protein, and a cell wall elicitor preparation derived from Phytophthora parasitica (Pp-elicitor) stimulate accumulation of the same gene transcripts and formation of the same pattern of furanocoumarins. Treatment of cultured cells and protoplasts with proteinase-digested Pp-elicitor identified proteinaceous constituents as active eliciting compounds in parsley. Similar to Pep- 25, Pp-elicitor induced effluxes of K+ and Cl- and influxes of protons and Ca2+. Concomitantly, as monitored in aequorin-transgenic parsley cell lines both elicitors induced an immediate increase in the cytoplasmic Ca2+ concentration up to sustained levels of 175 nM (Pp-elicitor) or 300 nM (Pep-25), respectively. The signature of the Ca2+ response differed greatly between the two elicitors tested. Extracellular Ca2+ proved essential for activation of an oxidative burst, MAP kinase activity and phytoalexin production by either elicitor. While Pp-elicitor induced a qualitatively similar spectrum of defense responses as did Pep-25, elicitor-specific quantitative differences in response intensity and kinetics suggest activation of a conserved signaling cascade through separate ligand binding sites.

PMID: 10945338 [PubMed - indexed for MEDLINE]

Accumulation of plastocyanin mRNA lacking 5' region in the green alga Pediastrum boryanum grown under copper-deficient conditions.

Nakamura M, Yoshizaki F, Sugimura Y.

Department of Biology, Faculty of Science, Toho University, Funabashi, Chiba, Japan. [email protected]

In the green alga Pediastrum boryanum NIES-301, plastocyanin accumulates under copper-sufficient conditions and cytochrome c6 accumulates under copper-deficient conditions. We cloned the cDNA which encodes pre-apoplastocyanin from P. boryanum cultured under the copper-sufficient condition. The deduced amino acid sequence of the pre-apoplastocyanin protein consists of 151 amino acid residues including a putative bipartite presequence of 53 amino acid residues. Southern blot analysis of P. boryanum genomic DNA indicated that pre-apoplastocyanin is encoded by a single nuclear gene. Northern blot analysis showed that copper-deficient cells accumulated a shorter form of the mRNA of pre-apoplastocyanin, which did not generate pre-apoplastocyanin in the wheat-germ translation system. The difference in size was ascribed to the absence of the 5' region in the mRNA of pre-apoplastocyanin obtained from the copper-deficient cells, which accounts for the absence of plastocyanin under these conditions. This phenomenon represents a novel regulatory mechanism, although details of the mechanism are not yet known.

PMID: 10750706 [PubMed - indexed for MEDLINE]

Calcium influx signals normal flagellar RNA induction following acid shock of Chlamydomonas reinhardtii.

Evans JH, Keller LR.

Department of Biological Science, The Florida State University, Tallahassee 32306-3050, USA.

Acid shock of Chlamydomonas results in flagellar excision and induction of flagellar protein RNAs. The magnitude of flagellar RNA accumulations after flagellar excision by mechanical shear depends on the extracellular Ca2+ concentration. In this report, we demonstrate that the magnitude and duration of flagellar RNA accumulations are signaled by an acid shock-induced Ca2+ influx. RNA accumulations were greater in cells acid shocked in 500 microM CaCl2 than in 200 microM CaCl2, although the accumulation durations were similar. RNA accumulations of lower magnitude and shorter duration were observed in cells in Ca2+-containing buffer treated with CdCl2. RNA accumulations were of still lower magnitude and shorter duration in cells shocked in buffer without added CaCl2 than in cells shocked in 200 or 500 microM CaCl2 or in the presence of CdCl2. RNA accumulations similar to those in cells shocked in buffer without added CaCl2 were measured in cells following acid shock in buffer containing 200 microM CaCl2 and supplemented with neomycin, ruthenium red, or LaCl3. Acid shock of the adf-1 mutant resulted in RNA accumulations of shorter duration and lower magnitude than those measured in adf-1 cells stimulated by mechanical shear. These results are consistent with an hypothesis that acid shock generates two genetically and pharmacologically distinct signals governing flagellar RNA induction; the first signal is independent of a Ca2+ influx and flagellar excision and results in low magnitude accumulations of short duration, and the second is a consequence of a Ca2+ influx and results in accumulations of high magnitude and long duration.

PMID: 9049267 [PubMed - indexed for MEDLINE]

Rapid accumulation of phosphatidylinositol 4,5-bisphosphate and inositol 1,4,5-trisphosphate correlates with calcium mobilization in salt-stressed arabidopsis.

DeWald DB, Torabinejad J, Jones CA, Shope JC, Cangelosi AR, Thompson JE, Prestwich GD, Hama H.

Department of Biology, Utah State University, Logan, Utah 84322-5305, USA. [email protected]

The phosphoinositide phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P(2)] is a key signaling molecule in animal cells. It can be hydrolyzed to release 1,2-diacyglycerol and inositol 1,4,5-trisphosphate (IP(3)), which in animal cells lead to protein kinase C activation and cellular calcium mobilization, respectively. In addition to its critical roles in constitutive and regulated secretion of proteins, PtdIns(4,5)P(2) binds to proteins that modify cytoskeletal architecture and phospholipid constituents. Herein, we report that Arabidopsis plants grown in liquid media rapidly increase PtdIns(4,5)P(2) synthesis in response to treatment with sodium chloride, potassium chloride, and sorbitol. These results demonstrate that when challenged with salinity and osmotic stress, terrestrial plants respond differently than algae, yeasts, and animal cells that accumulate different species of phosphoinositides. We also show data demonstrating that whole-plant IP(3) levels increase significantly within 1 min of stress initiation, and that IP(3) levels continue to increase for more than 30 min during stress application. Furthermore, using the calcium indicators Fura-2 and Fluo-3 we show that root intracellular calcium concentrations increase in response to stress treatments. Taken together, these results suggest that in response to salt and osmotic stress, Arabidopsis uses a signaling pathway in which a small but significant portion of PtdIns(4,5)P(2) is hydrolyzed to IP(3). The accumulation of IP(3) occurs during a time frame similar to that observed for stress-induced calcium mobilization. These data also suggest that the majority of the PtdIns(4,5)P(2) synthesized in response to salt and osmotic stress may be utilized for cellular signaling events distinct from the canonical IP(3) signaling pathway.

PMID: 11402204 [PubMed - indexed for MEDLINE]

Direct measurement of aluminum uptake and distribution in single cells of Chara corallina.

Taylor GJ, McDonald-Stephens JL, Hunter DB, Bertsch PM, Elmore D, Rengel Z, Reid RJ.

Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E9.

Quantitative information on the uptake and distribution of Al at the cellular level is required to understand mechanisms of Al toxicity, but direct measurement of uptake across the plasma membrane has remained elusive. We measured rates of Al transport across membranes in single cells of Chara corallina using the rare (26)Al isotope, an emerging technology (accelerator mass spectrometry), and a surgical technique for isolating subcellular compartments. Accumulation of Al in the cell wall dominated total uptake (71-318 microgram m(-2) min(-1)), although transport across the plasma membrane was detectable (71-540 ng m(-2) min(-1)) within 30 min of exposure. Transport across the tonoplast was initially negligible, but accelerated to rates approximating uptake across the plasma membrane. The avacuolate protoplasm showed signs of saturation after 60 min, but continued movement across the plasma membrane was supported by sequestration in the vacuole. Saturation of all compartments was observed after 12 to 24 h. Accumulation of Al in the cell wall reflected variation in inverted question markAl(3+) inverted question mark induced by changes in Al supply or complexing ligands, but was unaffected by pH. In contrast, transport across the plasma membrane peaked at pH 4.3 and increased when inverted question markAl(3+) inverted question mark was reduced by complexing ligands. Cold temperature (4 degrees C) reduced accumulation in the cell wall and protoplasm, whereas 2,4-dinitrophenol and m-chlorocarbonylcyanidephenyl hydrazone increased membrane transport by 12- to 13-fold. Our data suggest that the cell wall is the major site of Al accumulation. Nonetheless, membrane transport occurs within minutes of exposure and is supported by subsequent sequestration in the vacuole. The rapid delivery of Al to the protoplasm suggests that intracellular lesions may be possible.

PMID: 10889247 [PubMed - indexed for MEDLINE]

A study of rubidium accumulation in Euglena gracillis.

Brenner ML, Maynard DN.

PMID: 5978546 [PubMed - indexed for MEDLINE]

[Accumulation of thorium-234 in seaweed]

[Article in Russian]

Nazarov AB, Zesenko AIa.

PMID: 5149743 [PubMed - indexed for MEDLINE]

[Mechanisms of plutonium 239 and polonium 210 accumulation in the brown alga Ascophyllum nodosum and sea phytoplankton]

[Article in Russian]

Zlobin VS, Mokanu OV.

PMID: 5495588 [PubMed - indexed for MEDLINE]

[Dependence of coefficients of accumulation of strontium-90 in hydrobionts upon ash content]

[Article in Russian]

Kulebakina LG.

PMID: 5407925 [PubMed - indexed for MEDLINE]

[Coefficients of the accumulation of calcium, strontium and strontium-90 in various marine hydrobionts]

[Article in Russian]

Bachrin AA, Kulebakina LG, Polikarpov GG.

PMID: 5616350 [PubMed - indexed for MEDLINE]

[The accumulation of uranium and plutonium by seaweed]

[Article in Russian]

Zlobin VS.

PMID: 5983968 [PubMed - indexed for MEDLINE]

Environmental cadmium in Europe.

Jensen A, Bro-Rasmussen F.

FORCE Institutes, Division for Isotope Techniques and Analysis, Brondby, Denmark.

The present article reviews information from the latest 10 years concerning fate and exposure of cadmium in the environment, on ecotoxicological effects, and on critical pathways leading to human and environmental exposure. It emphasizes the situation within the Community of European Countries by referring to limit values used in the EEC and some of its member states for emissions to water, air and soil. Estimates have been made on total emission balances for the Netherlands, Denmark, and for the EEC as a whole. The balances show that 70-90% of all cadmium circulating in the Community is disposed of as waste in solid waste deposits. Production and use patterns are presently changing, as indicated by reduced consumption in recent years of cadmium for plating, stabilizers and pigments in several countries as a result of regulations. However, significant increases in consumption for cadmium-containing batteries have occurred, resulting globally in increasing trends for the total consumption and production. Cadmium in sediments is more mobile than described earlier. Aquatic organisms can be classified in order of decreasing accumulation: algae greater than molluscs greater than crustaceans greater than fish. There is no evidence of biomagnification of cadmium within marine or fresh water food webs. Cadmium may enter into plants via roots or by foliar adsorption following atmospheric deposition. Biomagnification in terrestrial food chains is not observed. The uptake into plants is plant specific. Within plants significant variations are seen with concentrations generally decreasing in the order: roots greater than leaves greater than fruiting parts greater than seeds. A compilation of cadmium in air, in the aquatic environment and in soil is given. A downward trend during the 1970s to mid-1980s seems to be evidenced from various Northern European studies on cadmium air concentrations as well as for deposition rates of cadmium. In rivers, the dissolved cadmium concentrations are generally found to be relatively low (10-500 ng/L). In seawater, cadmium concentrations are found at 0.5-10 ng/L in oceanic or open marine areas, while elevated concentrations are reported in more closed marine areas and especially in coastal zones close to polluted estuaries. In fresh water, lake sediments concentrations 3-30 times higher than the background concentrations are reported in the surface layers of sediments. A significant decrease in such pollution has been observed within the recent 10 years. For marine sediments, enrichment factors of two are found in sediments from open areas and locally even 5-10 times.(ABSTRACT TRUNCATED AT 400 WORDS)

Publication Types:

Review

Review, Academic

PMID: 1509176 [PubMed - indexed for MEDLINE]

Metal accumulation in the green macroalga Ulva fasciata: effects of nitrate, ammonium and phosphate.

Lee WY, Wang WX.

Department of Biology, The Hong Kong University of Science and Technology (HKUST), Clear Water Bay, Kowloon.

Coastal organisms are often exposed to both metal pollution and nutrient enrichment. The influences of major nutrients (nitrate, ammonium, and phosphate) on the accumulation of trace metals (Cd, Cr, Zn and Se) in Ulva fasciata were examined. The relative accumulation of metals was quantified by the kinetic measurements of accumulated metal concentration over a short exposure period (8 h). Our study demonstrated that macronutrients could markedly influence the rate of metal accumulation in the macroalgae. An increase in ambient nitrate concentration resulted in a significant increase in Cd accumulation rate, whereas the rate of accumulation of Cr and Zn was not greatly affected by the ambient nitrate level (between 10 and 100 microM). Zn uptake in nitrate-enriched macroalgae was, however, significantly higher than its uptake in N-starved macroalgae. The accumulation of Cd, Cr and Zn was not appreciably affected by the concentration of ammonium. Se accumulation was significantly inversely related to the ambient phosphate concentration, presumably due to the competitive inhibition by a high P concentration. Cr accumulation in the macroalgae increased significantly with increasing phosphate concentration. These data implied that the influences of major nutrients on cationic and anionic metal accumulation were highly metal-specific. The dependence of metal accumulation on major nutrients will appreciably affect our prediction of metal accumulation in macroalgae and the interpretation of biomonitoring data using the Ulva species.

PMID: 11669259 [PubMed - indexed for MEDLINE]

Adhesion of water-borne particulates on freshwater biota.

Sansone U, Belli M, Riccardi M, Alonzi A, Jeran Z, Radojko J, Smodis B, Montanari M, Cavolo F.

ANPA-National Environmental Protection Agency, Roma, Italy.

The retention of suspended particles transported by river flow on surfaces of freshwater plants is a potentially important process in the contamination of aquatic biota. Field experiments have been performed to test the role of benthic algae (periphyton) in trapping inorganic suspended solids transported by the river water and to discriminate between the caesium content of periphyton caused by the adherence of inorganic solids and by the active uptake inside the organisms. The contribution of caesium of suspended solids adhering to biotic surfaces was estimated by determining the scandium content (scandium method). The scandium method was used because this element is geologically ubiquitous in soils and it is not taken up actively by plants and other organisms. The mass of suspended particles retained on the surfaces of microorganisms growing on submerged substrates were determined by comparing the scandium content of suspended material with that in algal communities. Neutron activation analysis was used as the analytical method for determination for both scandium, and caesium. The results indicate that the suspended particle fraction can contribute up to 80% of the caesium contamination of periphyton samples. Active caesium uptake and accumulation by aquatic biota represents the remaining 20% of the total caesium contamination.

PMID: 9770322 [PubMed - indexed for MEDLINE]

Temporal changes of 210Po in temperate coastal waters.

Wildgust MA, McDonald P, White KN.

School of Biological Sciences, University of Manchester, UK. [email protected]

The temporal variation of Polonium-210 (210Po) was examined in coastal sea water, the mussel Mytilus edulis, the winkle Littorina littorea and green alga Ulva lactuca in order to investigate the entry of 210Po into the marine food chain. More than 99% of 210Po in the water column occurred in the particulate phase. Dissolved 210Po concentrations peaked during the spring phytoplankton bloom and it is suggested this is related to preferential scavenging of 210Po by the increased numbers of bacteria, viruses and small dissolved particulates. Changes in L. littorea 210Po specific activity are thought not to be related to food, but to a drop in body weight following spawning. Much of the 210Po accumulated by M. edulis was located in the digestive gland. The specific activity of 210Po in the digestive gland of M. edulis was shown to be strongly correlated with changes in sea water suspended particulate specific activity. Examination of other trace metal (Ag, Al, As, Ca, Cd, Cr, Co, Cu, Fe, Hg, K, Mg, Mn, Na, Ni, Sb, Se, Sn and Zn) variations in the digestive gland revealed that class B and borderline metals had a strong positive correlation with 210Po. On-going work is investigating whether the accumulation and loss of 210Po is affected by the presence of metallothioneins.

PMID: 9646514 [PubMed - indexed for MEDLINE]

Nutrient profiles in the everglades: examination along the eutrophication gradient.

Vaithiyanathan P, Richardson CJ.

Duke University Wetland Center, Loxahatchee, FL 33470, USA.

We examined the concentration profiles of nutrients in the surface water, soil and pore water along the eutrophication gradient of the Water Conservation Area-2A (WCA-2A) in the northern Everglades. Phosphorus levels in the surface waters contributed by the agricultural runoff showed an exponential decrease downstream of the inflow structures attaining background values of 7-12, 7-9 and 5-6 micrograms l-1 of TP, TDP and PO4-P, respectively, at distances of 8-10 km. The pore water PO4-P concentration in the oligotrophic areas ranged between 5 and 10 micrograms l-1. Molar ratios of dissolved inorganic N and P suggest a possible switch in nutrient limitation in the surface water from P in the oligotrophic areas to N in the eutrophic areas (DIN:DIP approximately 5). External nutrient loading has also contributed to a three- to four-fold increase in soil TP concentration and enhanced pore water PO4-P in the northern marshes. Unlike P, C and N concentration in the soils remained fairly uniform along the eutrophication gradient. 210Pb dating of soil cores suggests that the increase in soil P concentration (from < 500 to 1500 micrograms g-1) and P accumulation rate (from 0.06 to 0.46 g P m-2 per year) at the eutrophic site correlates with the installation of inflow structures in 1960-1963 through which agricultural drainage from the Hillsboro canal enters the marshes. Organic P makes up 70-90% of the total P in the soils as uptake by algae and macrophytes is the primary mechanism of P removal in these wetlands. Calcium supply from the underlying bedrock suggested from the surface and pore water chemical profiles has important consequences for P-cycling in the Everglades as Ca-bound P is the major form of inorganic P storage in the soils.

PMID: 9352671 [PubMed - indexed for MEDLINE]

Accumulation of copper, lead, manganese and iron by field populations of Hydrodictyon reticulatum (Linn.) Lagerheim.

Rai UN, Chandra P.

Aquatic Botany Laboratory, National Botanical Research Institute, Lucknow, India.

The potential of 'water-net' Hydrodictyon reticulatum to accumulate copper, lead, manganese and iron was determined in seven polluted water bodies having different physicochemical characteristics. The lead accumulation was linearly related with ambient concentration whereas in case of copper, manganese and iron it was maximum at lowest ambient level of metals. Investigations on response of alga to various concentrations of test metals under single metal treatments revealed that the algal cells are saturated at high equilibrium concentration of greater than 0.5 (lead), greater than 2.5 (copper and iron) and greater than 5.0 (manganese) mg/l. Alkaline pH favoured accumulation of these metals under field conditions. Alga showed high concentration factor (Cf) for all the metals both under field and laboratory conditions. However, Cf value was higher in case of manganese and iron in natural populations. Results indicate the possibility of using this alga in waste water treatment programmes.

PMID: 1615306 [PubMed - indexed for MEDLINE]

The adsorption kinetics of metal ions onto different microalgae and siliceous earth.

Schmitt D, Muller A, Csogor Z, Frimmel FH, Posten C.

Engler-Bunte-Institute, Department of Water Chemistry, Engler-Bunte-Ring 1, Universitat Karlsruhe, 76131 Karlsruhe, Germany.

In the present work the adsorption kinetics of the six metal ions aluminum, zinc, mercury, lead, copper, and cadmium onto living microalgae were measured. The freshwater green microalga Scenedesmus subspicatus, the brackish water diatom Cyclotella cryptica, the seawater diatom Phaeodactylum tricornutum, and the seawater red alga Porphyridium purpureum were the subject of investigation. In most cases the adsorption rate of the metals could be well described by using the equation of the Langmuir adsorption rate expression. Inverse parameter estimation allowed the determination of the rate constants of the adsorption process and the maximum metal content of the algae. The highest values for the rate constant were obtained for Porphyridium purpureum followed by Phaeodactylum tricornutum. High values for the maximum content were obtained for Cyclotella cryptica and Scenedesmus subspicatus. The maximum rate constant was 24.21 h-1 for the adsorption of Hg to Porphyridium purpureum whereas the maximum metal content (0.243 g g-1) was obtained for Zn on Cyclotella cryptica. A comparison of these values with those obtained for the mineral siliceous earth exhibiting low maximum content and high adsorption rates reveals that the mechanism of adsorption onto the algae is a mixture of adsorption and accumulation.

PMID: 11228977 [PubMed - indexed for MEDLINE]

[Formation and action of epimerase from Azotobacter vinelandii]

[Article in German]

Wetzler C, Behrens U.

After exhaustion of the C-source, terminating the accumulation of the extracellular polysaccharide, the excretion of the epimerase is increased, accordingly the moiety of guluronosyls of the alginate is augmented. Epimerization reactions with an epimerase preparation with commercial alginates from algae lead to higher conversion rates than with alginate from Azotobacter vinelandii. It is reasoned that the acetyl groups of bacterial alginate perform a steric hinderance. Because of the small amount of guluronosyls in Azotobacter alginate, these alginates do not form gels with Ca++.

PMID: 7072263 [PubMed - indexed for MEDLINE]

Biochemical studies on sporulation in blue-green algae. II. Factors affecting glycogen accumulation.

Kanta S, Sarma TA.

Inorganic nitrogens sources like nitrate, nitrite enhanced sporulation and glycogen accumulation in Anabaena sp. but ammonium chloride neither influenced sporulation nor glycogen accumulation. Acetate and citrate also stimulated early sporulation and glycogen level was higher over nitrogen free control. Nitrogen and carbon sources in combination proved to be useful in inducing early sporulation and increased content of glycogen. Phosphate and calcium also affected glycogen accumulation significantly, although, the sporulation was found to be of the same order as in nitrogen free medium. Sulphate initiated early sporulation, the mechanism of which is not known.

PMID: 6776695 [PubMed - indexed for MEDLINE]

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