1. Microbiology – study of small life
Viruses and Monera
Microbiology – study of small life

2. Virus – “poison”
Alive? – we are not sure. Consensus is they are not alive, they meet some but not all of the traits of life

3. Why study?
They affect living things, also helps understand difference between life and non-life

4. Composition and Structure

5. Composition and Structure
Nucleic acid – DNA or RNA, genetic material

6. Composition and Structure
Protein coat - (capsid) surrounds and protects the nucleic acid

7. Composition and Structure
Envelope – additional protective coating, contains spikes that bind to sites on a cell

8. Classification
Shape
Host they infect
How they function

9. Shape – the arrangement of proteins in capsids

10. Helical
RNA coils tightly inside the long, narrow capsid

11. Binal
Two parts, polyhedral capsid and a helical tail

12. Polyhedral Multifaceted geometric appearance
Adenovirus is one that causes colds

13. Filovirus
No distinct shape, threadlike or looped at end

14. What shape is it?

15. What shape is it?

16. What shape is it?

17. What shape is it?

18. Host – who they infect

19. Animal
infect only animals

20. Plant
Infect only plants

21. Bacteria
(bacteriophages) Infect only bacteria

22. Other
Can infect many different hosts or only certain species of that host

23. Function How they behave or work inside a host
Normal viruses and Retroviruses

24. Retrovirus
“reverse” virus, turns its RNA to DNA

25. Discovery – found by surprise, looking for the cause of tobacco mosaic disease

26. Dmitri Ivanovsky
Must be caused by unusually small bacteria or poisons from bacteria
Russian Biologist
1892

27. Martinus Beijerinck
Caused by something smaller than bacteria, an infectious agent he called virus
Dutch Biologist
1897

28. Still unsure where viruses came from, but have discovered many diseases since that have been caused by viruses

29. Viral Diseases in Humans:
Common cold

31. Viral Diseases in Humans:
Measles
infection of the respiratory system, spread through air, fever, cough, red eyes, rash

32. Viral Diseases in Humans:
Warts

33. Viral Diseases in Humans:
AIDS
Auto immune deficiency syndrome – spread through body fluids or blood

34. Viral Diseases in Humans:
Mono
Spread through saliva or mucus, fatigue, swollen lymph nodes, enlarged spleen

35. Viral Diseases in Humans:
Polio
damage the nervous system and cause paralysis
Enters mouth by contaminated hands with feces

36. Viral Diseases in Humans:
Viral pneumonia
Inflammation of the lungs, cough with mucus, fever, chills

37. Viral Replication – do not reproduce, no cell division, need a host

38. Host
An organism that shelters and nourishes something

39. Lytic Life Cycle
Virus rapidly kills the host cell (lyses = break apart)

40. Lytic Life Cycle
Attachment – virus sticks to cell and enzymes eat a hole in host cell membrane

41. Lytic Life Cycle
Entry – viral DNA enters host cell and takes control

42. Lytic Life Cycle
Replication – viral DNA instructs host to make copies of itself and protein coats

43. Lytic Life Cycle
Assembly – viral parts are put together to form new viruses

44. Lytic Life Cycle
Release – host cell bursts releasing new viruses

45. Then it all starts again…
But sometimes…

46. Lysogenic cycle
Virus doesn’t immediately kill the host cell

47. Lysogenic cycle
Attachment – virus sticks to cell and enzymes eat a hole in host cell membrane

48. Lysogenic cycle
Entry – viral DNA enters host cell and inserts into chromosomes

49. Lysogenic cycle
Replication – host cell divides, replicating viral DNA with own DNA

50. Lysogenic cycle
Stimulus – something causes the viral DNA to separate from chromosome and enter Lytic cycle
Without a stimulus, the viral DNA stays dormant in the cell’s chromosomes

51. Lysogenic cycle
That’s how people with HIV can go years without showing symptoms of AIDS, and still pass the virus on to others

52. Non-viral Particles
Recently discovered particles that act like viruses
VIROIDS
PRIONS

53. Viroids
Just a nucleic acid (no protein coat)
Causes – plant diseases

54. Prions
Just a protein (no nucleic acid)
Causes – mad cows disease