1. Viruses and Bacteria

2. Not So Harmless In The News

3. Viruses Infectious agents No cell structure Contain DNA or RNA Non-living Obligate parasites

4. Properties of Viruses Can infect all forms of life Many infect only one species

5. Virus Size Extremely small Comparison –Human red blood cell = 10,000 nm –Plasma membrane width 30 nm

6. Virus Structure Nucleic acid core –DNA (double or single stranded) –RNA

7. Virus Structure Capsid = protein covering Some have envelope over capsid

8. Tobacco Mosaic Virus

9. Herpes Virus

10. Replication of Viruses Cannot multiply outside cells Uses cell organelles to multiply Process is called lytic cycle Lysogenic cycle –Long term relationship of cell & virus –Viral nucleic acid replicates as cell multiplies

12. Ways Viruses Cause Disease Can initiate cancer Can take over cell function

13. Cancer & Viruses Some viruses initiate cancer Virus causes cell changes Virus does not “carry” cancer

15. Viruses as Pathogens Disrupt cell functions Use cells to make more virus

16. Viral Infections Acute infection –Rapid onset –Run a course –Subside –Examples Common cold Influenza Measles Mumps Latent Infection –Infective agent present –Not manifesting disease –Causes latent infections –Examples Herpes HIV

17. Genital Herpes Common STD –More than 1 in 5 age 12 & over in U.S. –Caused by herpes simplex virus –Develops a few days after sexual contact –Spreads when virus is active –Lesions develop –Latent infections

19. Prions & Viroids Infectious agents Simpler than viruses

20. Prions Proteins that cause disease Only infectious agent with no nucleic acid Examples: –Bovine spongiform encephalopathy mad cow disease –Creutzfeldt-Jacob disease

21. Healthy Brain TissuePrion-infected Brain Tissue

22. Viroids Small strands of RNA No protein coats Replicated in host cells Known to cause plant diseases

23. Bacteria Prokaryotic cells Some harmful, some helpful Present virtually everywhere

25. Characters of Bacteria No membrane-bound nucleus No membrane-bound organelles

27. Modes of Nutrition in Bacteria Photoautotrophic Chemoautotrophic Hetrotrophic

28. Photoautotrophs Produce food via photosynthesis Green & purple bacteria, cyanobacteria Cyanobacteria probably oxygenated Earth’s atmosphere

29. Chemautotrophs Energy from inorganic molecules Manufacture growth factors –Carbohydrates –Fats –Proteins –Nucleic acids Important in nitrogen cycling

30. Heterotrophs Feed on other organisms Play key role in carbon cycling Many bacteria are decomposers Release CO 2 used by photosynthesizers

31. Archaea Prokaryotic cells Not bacteria None cause disease Often in harsh habitats

33. Reproduction in Bacteria Asexual binary fission

34. Bacterial Disease Attach to cells Cause tissue damage Some plant diseases Many human diseases

36. Syphilis Caused by spiral bacterium Sexually transmitted Curable with penicillin Can cause death if untreated

37. Stages of Syphilis Primary –Hard chancre sore –Becomes painful Secondary –6 weeks – months –Dispersed thru body –Lesions at other sites

38. Stages of Syphilis Latent stage –No symptoms –May last a lifetime Tertiary stage –New lesions – tumor-like –Paralysis and death

39. Gonorrhea Sexually transmitted May exhibit few symptoms Can cause sterility

40. Clamydia Most prevalent STI Can lead to sterility Grow only within other cells Bacteria is “energy parasite”