ch28-Bacteria%20&%20Archaea--hunter%20notes[1] - BLY...

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B L Y 1 2 2 A . H u n t e r f r o m C . S . M a j o r Chapter 27 – Bacteria and Archaea I. What Are the Bacteria and Archaea? A. Bacteria and Archaea make up the most diverse of the kingdoms. 1. Over 5000 species have been named and described. 2. Most microbes are bacteria or archaea. B. Bacteria and Archaea are the most abundant, ubiquitous organisms on Earth. 1. Humans have more bacterial cells living in and on them than they have cells of their own bodies. 2. One teaspoon of soil has billions of bacteria living in it. 3. A drop of seawater has more Prochlorococcus bacteria than a large city has people. C. Bacteria and Archaea live almost anywhere and eat almost anything. II. Why Do Scientists Study Bacteria and Archaea? A. A small percentage of bacteria that inhabit the human body are pathogenic and cause disease. 1. In the late 1800s Robert Koch hypothesized that bacteria may be responsible for causing infectious disease. a. He tested hypothesis by studying anthrax, which infects grazing animals. b. Koch developed four postulates required to establish a causative link between a specific microbe and a disease: (1) Microbe must be present in individuals suffering from the disease and absent in healthy individuals. (2) Organism must be isolated, grown in pure culture away from the host. (3) Injection of organisms from the pure culture into a healthy animal should cause the disease symptoms to appear. (4) The organism must then be isolated from the diseased animal, cultured again, and shown to be identical in size, shape, and color to the original organism. c. Koch demonstrated that for anthrax, all four postulates were true. d. Koch’s postulates became the basis for the germ theory of disease. (1) Germ theory forms the basis for modern medicine. (2) Germ theory states bacteria and viruses cause infectious diseases. 2. Antibiotics are molecules that kill bacteria. a. Since their development in the late 1920s, these drugs have been very useful in combating infectious disease. b. The recent evolution of drug-resistant bacterial strains has presented a new challenge in modern medicine. B. Bioremediation: The use of bacteria and archaea to clean up human pollution 1. Most pollution is caused by organic solvents and fuels leaking into water supplies. a. Most of these are hydrophobic and do not dissolve in water. b. If ingested by organisms living in soil and water, they pass through the food chain and can be toxic to eukaryotes in moderate to high amounts. 2. Sediments where these compounds accumulate can become anoxic—devoid of oxygen. a. Oxygen in these sediments is used up by decomposers. b. Once anoxic, the rate of decomposition decreases. 3. Biologists trying to clean up pollution face some problems: a. The slow rate of decomposition presents a problem for biologists trying to clean up the polluted sediment.
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This note was uploaded on 11/11/2009 for the course BLY 459 taught by Professor Obrien,j during the Spring '08 term at S. Alabama.

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ch28-Bacteria%20&%20Archaea--hunter%20notes[1] - BLY...

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