BIMM 120 Lecture18_ReadingGuide.053111

BIMM 120 Lecture18_ReadingGuide.053111 - Lecture 18...

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Lecture 18 – BIMM120.SP11 LECTURE 18 – May 31, 2011 (pp. 714-721; 725-730) IV. Animal - Microbial Symbioses 24.10 The Rumen and Ruminant Animals Ruminant Animals o Ruminants are herbivorous mammals that possess a special digestive organ, the rumen , within which cellulose and other plant polysaccharides are digested with the help of microorganisms Rumen Anatomy and Activity o The bulk of the organic matter in terrestrial plants is present in insoluble polysaccharides, of which cellulose is the most important o The digestive processes and the microbiology of the rumen have been well studied, in part because it is possible to create a sampling port, called a fistula, into the rumen of a cow or a sheep and remove samples for analysis Microbial Fermentation in the Rumen o Food stays in the rumen about 9-12 hours. During this period cellulolytic microorganisms hydrolyze cellulose to free glucose o The glucose then undergoes bacterial fermentation with the production of volatile fatty acids (VFAs), primarily acetic, propionic, and butyric , and the gases CO 2 and CH4 Rumen Bacteria o Anaerobic bacteria naturally dominate because the rumen is anoxic Dangerous Changes in the Rumen Microflora o Changes in the microbial composition of the rumen can cause illness or death to the animal o For example, an abrupt switch from a forage to a grain diet in a cow could cause abnormal growth of S. bovis , which elevates the levels of lactic acid in the cow’s rumen and can lead to acidosis Rumen Protists and Fungi o The rumen has, in addition to prokaryotes, a high concentration of ciliated protists o Anaerobic fungi also inhabit the rumen and play a role in ruminal digestive processes Other Herbivorous Animals: Cecal Animals o Cows and sheep are the most familiar ruminants o Goats, camels, buffalo, deer, reindeer, and elk are also ruminants o Although horses and rabbits are herbivorous mammals, they are not ruminants o Horses and rabbits have only one stomach but use an organ called the cecum , a digestive organ located posterior to the small intestine and anterior to the large intestine, as their cellulolytic fermentation vessel 24.11 Hydrothermal Vent Microbial Ecosystems 1
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Lecture 18 – BIMM120.SP11
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BIMM 120 Lecture18_ReadingGuide.053111 - Lecture 18...

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