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Unit 6 – Organismal Biology Part 1: Bacteria and Viruses

Unit 6 – Organismal Biology Part 1: Bacteria and Viruses. Are these viruses alive?. A “borrowed” life. Cannot reproduce Cannot carry out metabolic activity outside of a host Exist as “entities” between life-forms and chemical. Virus Structure.

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Unit 6 – Organismal Biology Part 1: Bacteria and Viruses

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  1. Unit 6 – Organismal BiologyPart 1: Bacteria and Viruses

  2. Are these viruses alive?

  3. A “borrowed” life • Cannot reproduce • Cannot carry out metabolic activity outside of a host • Exist as “entities” between life-forms and chemical.

  4. Virus Structure • Nucleic acid arranged as single linear or circular molecules. • Double-stranded DNA • Single-stranded NA • Double-stranded RNA • Single-stranded RNA

  5. Virus Structure • Capsid – protein coat that covers the viral genome. • Varies in shape • Built from capsomere protein subunits

  6. Virus Structure • Envelope • Accessory structure (not found in all) • Membrane w/proteins that surrounds envelop • Derived from host cell

  7. Virus Reproduction • Limited by the host range • Prokaryotic cells (bacteria) • Eukaryotic cells (plants, animals) • Lock-and-key recognition mechanism (specificity)

  8. General Features • Virus binds to host cell and viral genome is inserted • Mechanism varies: • Inject DNA • Endocytosis (taken in) • Fusion of viral envelop with host membrane

  9. General Features • Once genome is inside, viral proteins take over control • Host provides raw materials and energy to make more viruses • New viruses exit the cell, damaging or killing it • This all varies…based on which type of host the virus infect!

  10. 2 3 1 4

  11. Reproductive Cycles of Bacteriophages • Phages infect only bacteria • Two alternative mechanisms: • Lytic Cycle  Ends in host death • Lysogenic Cycle Replication without host death

  12. Lytic Cycle If phage only reproduces this way, it is considered virulent phages. 1 2 5 3 4

  13. Phages that use both lytic and lysogenic are considered temperate phages. Lysogenic Cycle 1 6 2 3 7 5 4

  14. Classes of Animal Viruses

  15. Classes of Animal Viruses

  16. Classes of Animal Viruses

  17. Classes of Animal Viruses

  18. Classes of Animal Viruses

  19. Classes of Animal Viruses

  20. Retroviruses • Highly complex reproductive cycle • Have an enzyme (reverse transcriptase)  transcribes RNA template into DNA (opposite direction!) • HIV causes AIDS (acquired immunodeficiency syndrome)

  21. Viral Disease in Animals • Some cause host to produce toxins • Some have toxic molecular components (envelop proteins) • Difficult to treat once infection occurs • Minimal success with antiviral drugs

  22. Vaccines • Tool for preventing infection • Harmless variant or derivative of a pathogen • Stimulates immune system response • Main types • Killed  Previously virulent micro-organisms • Attenuated  Live micro-orgs w/virus that has been cultivated to disable virulent properties

  23. Emerging Viruses • Appear suddenly, new to medical science • Examples: HIV (1980’s); Ebola • Contributing factors: • Mutation of existing viruses • Spread from small, isolated population (globalization, travel, technology) • Spread of existing animal viruses to humans Example: Spanish Flu pandemic (birds  humans)

  24. Viroids and Prions • Simple infectious agents • Viroids Circular RNA molecules that infect plants • Abnormal growth patterns • Prions  Infection proteins that infect animals • Degenerative brain diseases (scrapie in sheep, mad cow, Creutzfeld-Jakob in humans) • Transmitted in food

  25. Viroids and Prions • Prions  Infection proteins that infect animals • Degenerative brain diseases • Scrapie(sheep) • Mad cow • Creutzfeld-Jakob (humans) • Kuru (humans) • Transmitted in food • Example: Beef to human; cannibalisms (New Guinea)

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