Species in the Cytophagagroup digest polysaccharide substrates like cellulose or chitin• Organisms in the Cytophagagroup 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 environmentLeft: transmission electron micrograph showing attachment of the cellulose-digesting bacterium Sporocytophaga myxococcoidesto cellulose fibers. Right: Clear areas in a cellulose-agar plate where Cytophaga hutchinsoniihas broken down cellulose.
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(C6H12O6)n+ Pi →(C6H12O6)n-1+ glucose 1-phosphatePolysaccharides 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.