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Unit 6 – Organismal Biology Part 1: Bacteria and Viruses

Unit 6 – Organismal Biology Part 1: Bacteria and Viruses. Domains of Life. Archaea. More closely related to eukaryotes than bacteria Extremophiles Extreme halophiles (high saline environments; Great Salt Lake, Dead Sea)

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Unit 6 – Organismal Biology Part 1: Bacteria and Viruses

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  1. Unit 6 – Organismal BiologyPart 1: Bacteria and Viruses

  2. Domains of Life

  3. Archaea • More closely related to eukaryotes than bacteria • Extremophiles • Extreme halophiles (high saline environments; Great Salt Lake, Dead Sea) • Extreme thermophiles (very hot environments; special DNA/proteins adaptations; volcanic springs, deep-sea vents

  4. Archaea • Methanogens • Strictly anaerobic; use CO2 to oxidize H2 and release methane as a waste product (swamps, marshes)

  5. Bacteria – Majority of Prokaryotes • Proteobacteria (large group, diverse) • Chlamydias (animal cell parasites) • Spirochetes (heterotrophs; syphilis, Lyme disease)

  6. Bacteria – Majority of Prokaryotes • Cyanobacteria (photoautotrophs; base of food chain in aquatic ecosystems; endosymbiosis leading to eukaryotic chloroplasts) • Gram-positive bacteria (simple cell walls; large group, highly diverse; tuberculosis, anthrax)

  7. Prokaryotic Cells • Primarily unicellular • Less complex than eukaryotic cells • No membrane-bound organelles • Lack a nucleus

  8. Prokaryotic Cell Structure • Cell wall (peptidodoglycan or other proteins/carbohydrates) • Capsule: Sticky covering of the cell wall(protection, attachment) • Fimbriae & sex pili (pilus): Hair-like proteins (attachment, pull cells together)

  9. Prokaryotic Cell Structure • Flagella (motility, taxis) • Specialized membranes (metabolic functions) • DNA • Chromosome located in nucleoid region • Plasmids (small rings of DNA)

  10. Prokaryotic Cell Shapes Bacilli (rods) Spirals Cocci (spheres)

  11. Metabolic Diversity • Photoautotrophs • Use sunlight energy to convert inorganic carbon • Chemoautotrophs • Oxidize chemicals (H2S, Fe) to convert inorganic carbon

  12. Metabolic Diversity • Photoheterotrophs • Use sunlight energy but need carbon in organic form • Chemoheterotrophs • Must consume organic molecules for energy and carbon source

  13. High Genetic Diversity (1) Rapid Reproduction • Asexual • Binary fission (offspring genetically identical to parent) • High mutation rate due to fast reproduction – New alleles

  14. High Genetic Diversity (2) Genetic Recombination • Combining DNA from two sources, 3 ways this happens…

  15. High Genetic Diversity • Transformation: • Uptake of foreign DNA from surroundings • Cell surface proteins recognize external DNA

  16. High Genetic Diversity • Transduction: • Horizontal gene transfer • DNA carried by bacteriophages (viruses)

  17. High Genetic Diversity • Conjugation: • Two cells joined by sex pilus • Mating bridge forms • Plasmid and chromosomal DNA can be transferred

  18. Roles in the Biosphere • Chemical recycling (decomposers) • Ecological interactions • Mutualism (N-fixing bacteria in root nodules) • Commensalism (e.g. 150 species live on your body surfaces  You provide food, they don’t harm) • Parasitism

  19. Impacts on Humans • Pathogenic bacteria • Cause about half of all human diseases • Produce poisons that cause illness • Exotoxins (secreted proteins) • Cholera • Botulism • Endotoxins (components of outer member; released when cell dies) • Salmonella

  20. Impacts on Humans – Not all bad!! • Research and Technology • Dairy industry (convert milk to cheese, yogurt) • Transgenic organisms  Genetic engineering • Bioremediation (removing pollutants from soil, water, air) • Used to make natural, biodegradable plastics • Produce hormones, antibiotics, vitamins

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