Bacteria & Viruses Chapter 21
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Transcript of Bacteria & Viruses Chapter 21
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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