2. Bacteria and Viruses AP Biology

3. Bacteria Very diverse Most abundant Prokaryotic Single chromosome; some have a plasmid Usually a cell wall Prokaryotic fission Great diversity in metabolism

4. Three Shapes Coccus—pl. coccispherical Bacillus—pl. bacillirod Spirillum—pl. spirillaspiral

5. Three Shapes

8. bacillus coccus

9. Three Shapes Diplococcus: chain of two Streptococcus: chain of many Tetrad: ball of four Sarcinae: larger ball Staphylococci: bunch of grapes

10. Three Shapes

14. Typical Cell

16. Gram Stain Bacteria are often identified as gram positive or gram negative This refers to their reaction to a staining method developed by Hans Christian Gram The structure of the cell wall determines the response + -

17. Gram Stain Gram positive appears purple or blue because the cell wall contains more peptidoglycan, which holds the violet stain. Gram negative appears pink or red. These have less peptidoglycan, which does not hold the violet dye. After the violet stain, they are rinsed in a red dye. The gram negative pick up only the second color.

18. Gram Stain

20. Prokaryotic Fission DNA is copied New cell membrane and new cell wall sections are made Cells separate

21. Prokaryotic Fission

22. Conjugation A tube connects the two bacteria The plasmid is replicated and transferred to the recipient cell

23. Classification Eubacteria: most abundant; now includes the blue- green algae and other monerans Archaebacteria: three groups based on metabolism

24. Viruses Are they alive? Do they exhibit the characteristics of life? What diseases do they cause?

25. Viruses Non-cellular Infectious agent Consist only of protein coat surrounding genetic material; coat contains proteins that bind with a receptor protein Genetic material can be DNA or RNA Range from 4 genes to several hundred genes

26. Viruses 4 typical body plans Helical Polyhedral-many sided coat T-even Enveloped Page 356

27. Viruses Cannot reproduce itself Must have a host cell Mutates frequently, outer protein coat changes That’s why we can’t make some vaccines and why we get some illnesses over and over again RNA viruses are called retroviruses; They must make cDNA from RNA and then proceed with replication

28. Viruses Viruses can attack animal cells, plant cells, and bacterial cells Viruses which attack bacteria are called bacteriophages, or phages Notice different types by shape

29. Viral reproduction in host cells Virus matches a receptor on host cell membrane Enters by endocytosis Directs replication of viral DNA and the manufacture of new viruses Damages or destroys the cell, resulting in symptoms

30. Viruses Replication in phages takes one of two pathways: lytic or lysogenic Lytic progresses right away Lysogenic may be latent and reactivated later

31. Viruses

32. Lytic cycle in a human cell

33. Viruses Lyse means “to burst” The lytic cycle always results in the death of the host cell Page 358 in text Computer generated picture of the polio virus

34. Smaller than Viruses Prions are small proteins that cause diseases of the nervous system—Mad Cow Disease Viroids are tightly folded strands or circles of RNA that resemble introns— mostly plant diseases Prions

35. Viroid plant infections

37. Influenza virus