Bacteria & Viruses

Chapter 21

Bacteria vs. Viruses Bacteria

Fully functioning cellular organisms Lack a nucleus Reproduce asexually - binary fission

Viruses Obligate intracellular parsites Reproduce inside bacteria, plant cells, animal

cells capsid

Bacteria vs. Viruses

Virus Bacteria

Bacteria – Gram Stains Gram-positive retain stain and appear purple

Have thicker layer in cell wall. Gram-negative do not retain stain and take

second pink stain instead.

Gram StainsPhylum Shape Motility Metabolism Gram

reacionCyanobacteria Bacilli,

CocciGliding, some non-motile

Aerobic, photosynthetic autotrophic

Gram-negative

Spirochetes Spirals Corkscrew Aerobic, and anaerobic; heterotrophic

Gram-negative

Gram-Pos Bacilli, cocci

Flagella; some non-motile

Aer/anaer.; heterotrophic, photosynthetic

Mostly gram-positive

Proteobacteria Bacilli, cocci, spiral

Flagella; some non-motile

Aer/anaer.; heterotrophic, photosynthetic autotrophic

Gram-negative

Bacteria: Key Characteristics Single-celled Prokaryotic Oldest living organisms Most common type of prokaryote

Bacteria Classification Nutrition Reactivity to oxygen Archaebacteria vs Eubacteria

Bacteria Classification - Nutrition Autotrophs

Photoautotrophs: photosynthetic autotrophs produce energy from light (blue-green algae)

Chemoautotrophs: produce energy from inorganic substances

Heterotrophs Bacteria that feed off of hosts

More Bactiera Nutrition - Heterotrophic Prokaryotes

Most free-living bacteria are chemoheterotrophs that take in pre-formed organic nutrients

As aerobic sapotrophs, there is probably no natural organic molecule that cannot be broken downby some prokaryotic species

Bacteria Classification: Reactivity to Oxygen

Obligate Aerobes: requires oxygen for respiration & growth

Obligate Anaerobes: oxygen serves as a poison – must avoid!

Facultative Anaerobes: can use oxygen if available but can also survive without it

Bacteria Classification:Archaebacteria vs Eubacteria

Archaebacteria Live in extreme environments

Extreme Halophiles: “salt lovers” live in environments w/ high salt concentration

Methanogens: bacteria that produce methane as a waste product

Thermoacidophiles: bacteria that love hot acidic environments

Types of Archaea Methanogens: live

under anaerobic environments where they produce

methane (eg marshes) Halophiles: require high

salt concentrations (eg Great Salt Lake)

Thermoacidophiles: live under hot,

acidic environments (eg geysers)

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Bacteria Classification:Archaebacteria vs Eubacteria

Moderate environments Categorized according to shape, motility, cell-wall

composition, pathogenic nature Proteobacteria Gram-positive bacteria Gram-negative bacteria Cyanobacteria Spirochetes Chlamydias Chemosynthetic bacteria Nitrogen-fixing bacteria****BE ABLE TO DESCRIBE EACH OF THE ABOVE BACTERIA!!

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Structure of Prokaryotes Outer wall strengthened by

peptidoglycon (molecule containing amino disacharride & peptide fragments

Some move by use of flagella Adhere to surfaces by means

of fimbriae

Reproduction in Prokaryotes Reproduce asexually through binary fission Mutations are chief means of genetic

variation

Kingdom Archaebacteria First discovered in extreme environments Methanogens: Harvest energy by converting H2

and CO2 into methane gas Anaerobic, live in intestinal tracts

Extreme halophiles: Salt loving live in Great Salt Lake, and Dead sea.

Thermoacidophiles: Live in acid environments and high temps. Hot Springs, volcanic vents

Kingdom Eubacteria Spirillum – spiral-shaped Bacilli – rod-shaped Cocci – round or spherical

Viruses Noncellular parasitic agent consisting of an

outer capsid and an inner core of nucleic acid

Have DNA or RNA genome, but can only reproduce by using the metabolic machinery of a host cell

Viral Structure Shape: varies from theadlike to polyhedral All viruses have same basic anatomy: outer

capsid with protein subunits & inner core of nucleic acid

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Categorizing Viruses Type of nucleic acid

DNA or RNA (not both) Single-stranded or double-stranded

Size and shape Presence or absence of an outer envelope

Viruses: Parasitic Nature Obligate intracellular parasites Host Specific: infect a variety of cells Viruses can mutate Viruses evolve & reproduce, but they are

not obligate intracellular parasites – they only grow inside their specific host cells

Lytic Cycle & Lysogenic Cycle

Lytic Cycle 5 Stages

1. Attachment: capsid combines with receptor

2. Penetration: viral DNA enters host

3. Biosynthesis: viral components are synthesized

4. Maturation: assembly of viral components

5. Release: new viruses leave host cell

Lysogenic Cycle Viral DNA integrated into host DNA The phage becomes a prophage that’s

integrated into the host genome Bacteriophage (phage): viruses that parasitize

bacteria Phage may reenter lytic cycle; reproduction

and release of the virus then occur

Viroids and Prions Viroids- naked strands of

RNA, directs the cell to make more viroids

Prions- (proteinaceous infectious particles), newly discovered disease agents that differ from viruses and bacteria

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