Chapter 20 – Bacteria & Viruses

1. Chapter 20 – Bacteria & Viruses

2. History • Iwanowski and Beijernick (1890’s) • Worked on Tobacco Mosaic Virus (infects tobacco and tomato leaves). • Creates mosaic pattern on leaves. • Made a juice of the infected leaves and then put this juice through a filter. • Rubbed the filtered juice onto leaves. • Still became infected. • Concluded that whatever these disease causing particles were, they were very small (smaller than bacteria). • Named them viruses meaning “poison” in Latin.

3. Stanley (1935) • Purified TMV into a crystal. • Living particles don’t crystallize therefore, viruses are non-living pathogenic (disease causing) particles.

4. Viruses • Particles of nucleic acid, proteinand (sometimes a lipid envelope). • Obligate intracellular parasite (can only replicate within a living cell)

5. Structure of a virus • All viruses are: • Small – 20nm (polio virus) – 350nm (smallpox virus) • Single type of nucleic acid (RNA or DNA but never both) • Have a protein coat – capsid • Some have envelopes (madeof lipids)outside of capsid • Surface projections made up of lipids for attachment onto host cells • Are specific to their host

6. HIVRetrovirus Envelope Projections

8. Bacteriophage Capsid Infect E. coli bacteria Attach with tail fibers onto cell. Inject nucleic acid into cell Tail

9. The Lytic Cycle • Get in, get replicate and get out to invade other host cells • The cold, the flu, Rubella (German measles), mumps Release Attachment at Receptor site Entry Replication Assembly

10. The Lytic Cycleof Virus infection Attaches onto host cell Injects DNA into host cell Replication of Viral parts Reassembly of virons Lysis – bursting out Viruses that reproduce only by the lytic cycle are called Virulent

11. Lysogenic Infection • Virus embeds its DNA into hosts DNA which is replicated with host cell’s DNA. • Remains unnoticed for sometimes years • HIV, cold sores, chicken pox, hepatitis Prophage Attachment Integration Cell multiplication & Injection of nucleic acid Prophage remains unnoticed and not transcribed. If animal cells, then its called a Provirus such as with all the herpes viruses and HIV (HIV+)

12. Diseases caused by viruses • AIDS • The Cold • Measles • Mumps • Rubella • Chicken pox/Shingles • Small Pox • Hepatitis • SARS • The Flu • Ebola • HPV • Bird Flu • Polio GLEN!!

13. Vaccines (SHOTS!!) are small doses of either killed, altered or live viruses. Body builds up antibodies against viral proteins.

15. Polio and the Iron Lung

16. The Different forms of Viruses • Retroviruses– HIV. Contains RNA instead of DNA. Goes from RNA to DNA to RNA to protein. Normal is DNA to RNA to protein. • Prion – viral proteins that cause diseases. Scrapie in sheep degrades nervous system. Mad Cow disease (Bovine spongiform encephalopathy) in cows – puts holes into brain. • In humans, its Creutzfeld-Jakob disease & Kuru.

19. Bacteria

20. Eubacteria & Archaebacteria • Unicellular, • Prokaryotic cell (no nucleus or membrane bound organelles. • Have Ribosomes and a cell wall , • Single long, circular strand of DNA • Auto or Heterotrophic

21. Kingdom – Archaebacteria • Lack Peptidoglycan in cell wall • Extremophiles • On the same line of evolution as eukaryotes

22. Kingdom – Eubacteria • Larger of the two kingdoms • Have Peptidoglycan in cell wall • 3 basic shapes • Bacilli – Rod shaped. E. coli, Bacillus anthracis

23. Cocci – Spherical shaped. • Staphylococcus aureus, Streptococcus pyogenes Strepto – Chains Tetra - 4 Staphylo –clusters • Diplo – 2 • Spirilla – Spiral shaped. Spirochette, Syphilis

24. Basic Structure

25. BACTERIA SONG

26. Endospores • Produced by Gram + (usually Bacillus & Clostridium) • Dormant structure to survive adverse conditions (heat, cold, dryness). Bacillus anthracis

27. Reproduction • Asexually by binary fission. No genetic variation • Conjugation - Sexual reproduction method . Two bacteria form a conjugation bridge or tube between them. DNA is transferred from one bacteria to the other

28. Binary Fission and Conjugation

29. Bacteria and Humans • Pathogens – disease causing agents (Pathology – science of studying diseases) • Can produce poisonous toxins (poisons) like the botulism toxin • Destroy food crops • Food poisoning

30. To fight them: • Antibiotics interfere with the production of the cell wall or protein or DNA synthesis. Penicillin, tetracycline • Bacteria can mutate and become antibiotic resistant (often results from overuse of antibiotics) • Usually due to conjugation or Transformation

34. Helpful Bacteria: • Bacteria of decay - major decomposers (Saprophytes) • Symbiosis – Nitrogen Fixing bacteria - Convert atmospheric N2 to NH3, Rhizobium in root nodules of legumes • Fermentation: Food processing of sour cream, yogurt, buttermilk, wine, sauerkraut, pickles, cheese • Industrial – “oil eating bacteria”, mining gold, cleaning up pollutants - Bioremediation • Biotechnology

35. Diseases caused by bacteria • Anthrax • Botulism • Cholera • Cavities • Gonorrhea • Syphilis • Tetanus • Staph Infection (MRSA) • Food Poisoning • Lyme Disease • Diphtheria • Tuberculosis • Escherichia coli O157: H7 • Leprosy • Meningitis • Strep throat • Whooping cough (Pertussis)

36. Food poisoning • Results from decay of foods and production of toxins • 33 million people/yr get “stomach flu” • Seafood accounts for 20 – 25% of cases • 33% of all raw poultry tests + for Staphylococcus • 1 in every 200 eggs has Salmonella

38. 4 C’s of Food Safety Chill your foods Cook your food to the proper temperature Clean food and cooking surfaces Combat Cross Contamination