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Chapter 27 bacteria and archaea

Chapter 27 bacteria and archaea - Chapter 27 Bacteria and...

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Chapter 27: Bacteria and Archaea (Domain) -- bacteria and archaea are mostly unnamed and are the dominant life forms on earth. (very diverse, abundant, and found almost everywhere) --Bacteria, Archaea, Eukarya are the 3 domains --there are more bacterial cells living inside us outnumber the cells in our body. I. Why do biologists study bacteria and archaea? a. Bacteria and archaea characteristics: i. Unicellular ii. Prokaryotic—lack a cell membrane. Smaller simpler than eukaryotic cells. iii. Ancestral to eukaryotes. Very diverse because of this. b. Bacteria characteristics: i. Cells walls made of mostly peptidoglycan ii. Similar plasma membranes as eukaryotes iii. RNA polymerase and ribosomes distinct from Archaea and Eukarya c. Archaea characteristics i. Cell walls made of polysaccharides (not found in other 2 domains) ii. Unique plasma membrane iii. RNA polymerase and ribosome similar to eukaryotic ones d. Bacterial disease i. Pathogenic —bacteria that cause disease. (no archaea known to cause disease) 1. Only a small fraction of the many bacteria cause disease ii. Louis Pasteur—microorganisms like bacteria spoil milk and make wine iii. Robert Koche—bacteria is responsible for infectious disease. Koch’s 4 postulates that needs to be met to link a microbe to a disease: 1. Microorganism must be present in sick person and absent in healthy person. 2. Organism must be able to be isolated and grown in a pure culture away from the host organism 3. If organisms from the pure culture are injected into a healthy animal, the disease symptoms should appear 4. When the organism is isolated from the diseased animal and again grown in pure culture, it should be the same as the original organism.(size, shape, color) iv. Germ theory of disease —infectious diseases are caused by bacteria and viruses. v. Antibiotics —molecules that kill bacteria
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e. Bioremediation —the use of bacteria and archaea to degrade pollutants. i. Leaked organic compounds are hydrophobic and accumulate in sediments in water. They can be ingested by worms, clam, etc and be passed along to fish, humans, etc. Most of these compounds are toxic to eukaryotes. 1. Ex) ring structured compounds; chlorine atoms (dioxins) ii. Sediments where these compounds accumulate can become Anoxic lacking oxygen. 1. Aerobes and decomposers live together. If water currents are not strong enough to mix sediments, the decomposers (that ingest organic compounds) that are aerobes use up all of the oxygen, so the sediment becomes anoxic. This causes the rate of decomposition to slow because organisms have to use electron acceptors that are weaker than oxygen. iii. Challenges for cleaning up sites polluted with organic solvents and fuels: 1. Polluted sediments are usually anoxic, so decomposition rate is slow 2. At least some of the toxic compounds present are highly resistant to decomposition.
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