15 - PROKARYOTIC DIVERSITY BIOL 4125 SPRING 2009 LECTURE 15...

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Unformatted text preview: PROKARYOTIC DIVERSITY BIOL 4125 SPRING 2009 LECTURE 15 The Cytophaga, Flavobacterium, and Bacteroides Species in the Cytophaga group digest polysaccharide substrates like cellulose or chitin Organisms in the Cytophaga group are widespread in soil and water. Obligate aerobes that account for much of the cellulose digestion that occurs by prokaryotes in oxic environments. They hydrolyze and digest a number of polysaccharides, including agar (top). Species capable of cellulose degradation can be easily isolated by placing small crumbs of soil on pieces of cellulose filter paper laid on the surface of mineral salts agar (bottom). Note the clearing zones where cellulose has been degraded. Do not produce soluble extra-cellular cellulases and these enzymes remain attached to the cell envelope, which is why the cells must be attached to the substrate. Cellulose forms long fibrils, is largely insoluble, and is usually less rapidly degraded than other polysaccharides in the environment Left: transmission electron micrograph showing attachment of the cellulose-digesting bacterium Sporocytophaga myxococcoides to cellulose fibers. Right: Clear areas in a cellulose-agar plate where Cytophaga hutchinsonii has broken down cellulose. (C 6 H 12 O 6 ) n + Pi (C 6 H 12 O 6 ) n-1 + glucose 1-phosphate Polysaccharides formed inside the cell are broken down by hydrolysis; however, extracellular polymers are degraded by phosphorolysis. This involves the addition of inorganic phosphate and results in the formation of a hexose phosphate rather than the free hexose. Glucose 1-phosphate can be easily converted to glucose 6-phosphate (a key intermediate in glycolysis) and represents a net energy savings to the cell. Species of Cytophaga and Flavobacteria are motile but lack flagella Left: the gram-negative gliding bacterium Flavobacterium johnsoniae showing masses of cells gliding away from the center of the colony. Right: mutant strain showing typical colony morphology of nongliding bacteria. Model for how gliding motility may occur Tracks (yellow) are thought to exist in the peptidoglycan that connect cytoplasmic proteins (brown) to outer membrane proteins (orange) and propel them along the solid surface....
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This note was uploaded on 08/04/2009 for the course BIOL 4125 taught by Professor Christner during the Spring '08 term at LSU.

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15 - PROKARYOTIC DIVERSITY BIOL 4125 SPRING 2009 LECTURE 15...

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