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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.

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Bacteria & Viruses Chapter 21

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  1. Bacteria & VirusesChapter 21

  2. 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

  3. Bacteria vs. Viruses Virus Bacteria

  4. 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.

  5. Gram Stains

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

  7. Bacteria Classification • Nutrition • Reactivity to oxygen • Archaebacteria vs Eubacteria

  8. 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

  9. 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

  10. 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

  11. 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

  12. 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)

  13. 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!!***

  14. 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

  15. Reproduction in Prokaryotes • Reproduce asexually through binary fission • Mutations are chief means of genetic variation

  16. 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

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

  18. 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

  19. Viral Structure • Shape: varies from theadlike to polyhedral • All viruses have same basic anatomy: outer capsid with protein subunits & inner core of nucleic acid

  20. 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

  21. 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

  22. Lytic Cycle & Lysogenic Cycle

  23. 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

  24. 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

  25. 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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