Utilization of PPi as an Energy Source by a Clostridium sp

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The growth of an anaerobic, spore-forming rod we have isolated from the cockroach gut after enrichment on media containing PPi was stimulated by the presence of PPi. The doubling time decreased and cell yield increased proportionately to PPi concentrations of up to 0.35%. A similar stimulation of the growth of Desulfotomaculum sp. by PPi has been reported. The PPi-stimulated Clostridium sp. fermented a number of sugars with the production of hydrogen, acetate, and butyrate, with smaller amounts of ethanol and butanol being produced from some substrates. The fermentation products were not qualitatively changed by the presence of PPi, but significantly more hydrogen was produced. The organism contained several of the enzymes previously reported from Entamoeba sp. and Propionibacterium sp., in which PPi serves as a source of a high-energy bond in place of ATP. These include significant amounts of pyruvate-phosphate dikinase and phosphoenolpyruvate carboxytransphosphorylase. The activities of many of the catabolic enzymes of the organism, as well as of its phosphatases and pyrophosphatase, were similar whether it was grown in the presence or absence of PPi. The organism did not accumulate intracellular polyphosphate granules but stored large amounts of glycogen.

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