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Understanding Bacteria and Viruses: Nature, Role in Disease, and Control Methods

Explore the world of prokaryotes like E. coli, their shapes, movement, energy sources, and reproduction methods. Learn about bacteria in nature, nitrogen fixation, bacterial diseases, vaccines, and antibiotics. Discover how viruses infect hosts, the lytic and lysogenic phases, disease implications, and the unique characteristics of retroviruses like HIV.

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Understanding Bacteria and Viruses: Nature, Role in Disease, and Control Methods

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  1. Chapter 19 Bacteria & Viruses 19.1 Prokaryotes

  2. Single-celled • Lack nucleus • Smallest, most common microorganism

  3. Classification

  4. E. Coli bacteria • Eubacteria (D/Bacteria) • Larger kingdom; greater diversity • Cell wall w/peptidoglycan (carbo) • Shapes

  5. Archaebacteria (D/Archaea) • Extremist (anaerobic methanogens) • Cell wall w/out peptidoglycan • DNA sequence of key genes = eukaryotes Bacteria in hot springs Billion yr old cyanobacteria

  6. Identification • Shapes • Bacilli: rod-shaped • Cocci: spherical • Streptococcus: chains • Staphylococcus: clusters • Spirilla: spiral-shaped Streptococcus Staphylococcus

  7. Cell Walls • Gram + : single layer; stain purple • Gram - : double layer; stain pink (disease)

  8. Movement • Flagella: whip-like structure

  9. Energy • Autotrophs (make food) • Photoautotrophs: cyanobacteria (aerobic) • Chemoautotrophs: anaerobic • Heterotrophs (obtain food) Cyanobacteria

  10. Respiration • Obligate aerobes: respire/need O2 • Obligate anaerobes: ferment/killed w/ O2 • (C. botulinum) • Facultative anaerobes: resp/ferm Flesh eating bacteria Tetanus C. botulinum produces the potent nerve toxin that causes botulism.

  11. Reproduction • 20 min doubling time • Binary Fission: Asexual reproduction • DNA replicated & divides • Identical daughter cells

  12. Conjugation: Sexual reproduction • Genetic material exchange • Protein bridge forms between bacteria (pilli)

  13. Endospore • Internal wall enclosing DNA/cytoplasm • Remains dormant (months to centuries)

  14. 19.2 Bacteria in Nature • Decomposers • Recycle nutrients • Sewage treatment

  15. Nitrogen Fixation • Fixing N2 (air) to NH3 (ammonia=fertilizr) • Plants need N for AA to make proteins

  16. Disease • Pathogens • Tissue damage: tuberculosis (lungs) Table 19.6 Tissue specificity as a factor in infectious disease

  17. Botulism: no contraction (death by respiratory failure) Tetanus: permanent contraction (death by respiratory failure) • Toxins: salmonella, tetanus, botulism

  18. Vaccines: stimulate immune system • Antibiotics: block growth/reproduction

  19. Human Uses • Food; Industrial; Genetic engineering BLOCKING OUT GAS. Unlike the left tower, which uses chemicals, the tower on the right at this wastewater-treatment plant now uses bacteria-covered foam blocks (inset) to eliminate the hydrogen sulfide bubbling from treated sewage. Bacteria products for biological filters BLOCKING OUT GAS.This wastewater-treatment tower bacteria-covered foam blocks (inset) to eliminate the hydrogen sulfide bubbling from treated sewage.

  20. Controlling • Sterilization: Heat; Disinfectant • Food: Refrigerate, heat, seal, preserve

  21. 19.3 Viruses

  22. What is it? • Non-living; lack cells; need host to reproduce • Smaller/simpler than smallest cells • DNA/RNA core; protein coat (capsid)

  23. Infection • Species specific (bacteriophage = only bacteria)

  24. Lytic: host cell destroyed • Virus enters host (DNA/RNA injected) • Replicates using materials of host DNA • Host burst and releases many new virus Lytic Viral Reproduction Phase

  25. Lysogenic: uses host indefinitely • Virus embeds DNA (prophage) into host DNA • Replicated w/ host DNA • Will eventually becomes lytic Lysogenic Phase

  26. Disease • Vaccines: must receive before infection • Cancer: oncogenic virus • Disrupt cell growth/division

  27. Retrovirus: contain RNA • DNA copy made and inserts into host DNA • RNA to DNA (backwards) • AIDS

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