Exploring the Microscopic World: Viruses, Bacteria, Protists, Fungi

1. Viruses, Bacteria, Protists, Fungi 1. Viruses, viroids, prions

2. Virus • name means poison • term was used to describe pathogens in the late 1800s • viruses are noncellular infectious agents (nonliving)

3. A virus contains two parts: • protein coat-protects genetic material • nucleic acid (either DNA or RNA but not both)

4. Some examples: Ebola

5. Common cold

6. Polio

7. Rabies

8. Herpes

9. Measles

10. A virus cannot reproduce itself-it must enter a cell and take over • In a series of steps, like an assembly line, a host cell makes virus parts and puts them together.

11. Viruses are host specific: • Bacteriophages-attack only bacteria (because bacteria reproduce quickly these viruses are often used to study viruses.) • Animal viruses • Plant viruses (have to be able to breach the cell wall--often they hitch a ride on a piercing insect)

12. Other infectious agents: • Prions-small proteins or altered products of a gene (mad cow, scrapie)

13. Viroids-tightly folded strands or circles of RNA, no protein coat, cause plant diseases, resemble introns Potato plant viroid

14. Viral replication • 1. Attachment-virus attaches to host cell-recognized chemically • 2. Penetration-nucleic acid enters cell • 3. Replication and synthesis-host cell is directed to make virus parts • 4. Assembly-viral nucleic acid and protein are put together • 5. Release-cell bursts and releases viruses

15. Lytic cycle-above steps proceed rapidly after infection. Symptoms felt within a short time period. • Lysogenic cycle-virus enters a latent period, infection is delayed. Virus becomes part of cell DNA and is passed to other cells in mitosis. Eventually something triggers it to start lytic cycle.

17. Viruses with RNA Called retroviruses-enter a cell but first must make DNA before it can be replicated. (RNA serves as a template to form DNA)

18. Bacteria • The most abundant organisms • found everywhere (hot springs, volcanoes, snow) • prokaryotic, circular DNA • usually have a cell wall • reproduce by fission

19. A bacterial cell

20. Bacteria shapes • coccus-round • bacillus-rod • spirillum-spiral

21. Growth patterns • strep-chains • staph-clumps or clusters • diplo-in pairs • tetra-fours

22. Shape and Pattern together • Streptococcus • Staphylococcus

23. Bacteria size • Bacteria are the smallest of all cells. • They range from 1 to 10 micrometers • http://www.cellsalive.com/howbig.htm

24. Staining-for identification of the cell wall. • Gram stain-process of staining that involves several steps and 2 dyes. Identifies the bacteria by cell wall type. • purple is crystal violet-gram positive (cell wall is one thick layer) • red is safranine-gram negative (cell wall is 2 thin layers)

25. Gram negative rods • Gram positive cocci

26. Classification: • Originally classification was by shape, size, motility, staining, metabolism. • Now biochemistry is used-proteins and RNA are compared. This changes how bacteria were classified.

27. Types of bacteria • Eubacteria-most common • Archaebacteria-have different genes, ribosomes and lipids. Match to a common ancestor with eukaryotic cells

28. Bacterial growth and reproduction • growth is measured not in size of cell but in increase in the number of cells • in ideal conditions many bacteria can divide as fast as every 30 minutes (a few even as fast as 10) • fortunately, conditions are rarely ideal!

29. Fission • 1. Parent cell replicates its DNA. Both are attached to the cell membrane.

30. 2. Membrane grows so cell stretches and pulls two DNA apart.

31. 3. New cell wall material is deposited above the membrane and grows through the midsection. • 4. Results in 2 identical cells

32. Conjugation • Bacteria also contain plasmids-small circular DNA. • a sex pilus forms-donor cell hooks onto recipient cell and pulls it close • conjugation tube forms between them • plasmid DNA is transferred through the tube • replication of plasmid occurs in both • cells separate

34. Infectious diseases • infection-pathogen invades body, multiplies in cells and tissues • disease-result on the body of an infection • contagious-pathogen can be transmitted from person to person

35. epidemic-spreads rapidly for a limited time • pandemic-spreads in several places • endemic-prevalent in a particular area

36. Tetanus

37. Tuberculosis

38. Staph skin infections

39. MRSA-methicillin resistant staphylococcus aureus

40. Whooping cough

41. Bubonic plague

42. Protists • all are eukaryotic • classified by what they are not • may be photosynthetic • some are multicellular

43. Fungus like Protists • Water molds • Slime molds- • cellular • plasmodial

44. Animal like Protists • Sarcodina-some make shells, move by pseudopods • examples-ameba, radiolarians

45. flagellates • example-giardia • sporozoans-parasitic • example-plasmodium

46. Mosquito bites human, injecting saliva that contains Plasmodium sporozoites Plasmodium sporozoites Anopheles mosquito bites infected human and picks up Plasmodium cells Liver Infected liver cells burst, releasing Plasmodium cells that infect red blood cells Infected red blood cells burst, releasing Plasmodium cells; some can infect other red blood cells, and others can infect mosquitoes Red blood cells

47. Ciliophora-ciliates • example-paramecium

48. Plant like Protists • Euglenaphyta-both heterotrophic and autotrophic

49. Chrysophyta-golden algae-diatoms (shells)

50. Pyrrhophyta-marine, dinoflagellates, some make toxins (red tide)