Virus Structure

Composed of genetic material and protein

Contain either DNA or RNA

Protein capsid surrounds genetic material

Viral shapes: rod, spiral, cubical or many-sided

Smaller than bacteria

Virus Properties

Lack cytoplasm, cell membranes, and ribosomes

Do not grow or carry on metabolic activities

Contains only one type of nucleic acid

Contains few enzymes

Can be crystallized and reactivated

Virus Reproduction: Lytic Cycle

Attachment: virus attaches to specific host cell receptor sites.

Entry: virus injects DNA into the host cell.

Replication: viral DNA takes over the cell, directing production of viral DNA and proteins

Assembly: new viruses made

Release: lysis of bacterial cell

Virus Reproduction: Lysogenic Cycle

Attachment and Entry: Virus enters the cell as in the lytic cycle.

Provirus formation: Viral DNA attaches to host DNA.

Cell divides with viral DNA. No harm is done to the host cell.

External stimuli (x-rays or UV radiation) causes the virus to become virulent.

Virus Classification

Genetic material

DNA viruses

may begin producing RNA directly

may become part of host cell DNA

examples: small pox, warts, mononucleosis, cold sores, genital herpes

RNA viruses

may produce proteins directly

retroviruses: make DNA from viral RNA, then new DNA directs RNA synthesis

examples: Polio, rabies, mumps, flu, measles, HIV

Characteristics

Monerans are prokaryotic and unicellular

Three common shapes

coccus: round

bacillus: rod

spirillum: spiral

Growth patterns

staphylo: clusters

strepto: chains

diplo: pairs

Structure

Cell wall used for protection; maintains osmotic balance

Capsule surrounds cell wall for additional protection

Endospore: dormant structure that may form when environmental conditions are harsh

Reproduction

Binary fission

DNA in the cell replicates

Plasma membrane and cell wall grow inward

Cell pinches in two

Conjugation

bridge is formed between two cells

small portion of DNA is passed from one cell to another

Eubacteria

Heterotrophs: parasites or saprophytes

Photosynthetic autotrophs: use light to obtain energy. Example: cyanobacteria

Chemosynthetic autotrophs: use sulfur and nitrogen containing compounds for energy.

Archaebacteria

Anaerobic and autotrophic

Methane-producing bacteria: live in swamps, marshes, digestive tracts of animals

Salt-loving bacteria: live in salt lakes

Heat and acid-loving bacteria: live near underwater volcanoes, thermal vents, and hot sulfur springs

Significance

Produce nutrients

Used to produce dairy products

Used to make antibiotics

Degrade environmental hazards

Fermented meats

Sugar syrup production

Stain removers

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