Carbohydrate Metabolism inSpirochaeta stenostrepta

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Abstract
The pathways of carbohydrate metabolism inSpirochaeta stenostrepta, a free-living, strictly anaerobic spirochete, were studied. The organism fermented glucose to ethyl alcohol, acetate, lactate, CO2, and H2. Assays of enzymatic activities in cell extracts, and determinations of radioactivity distribution in products formed from14C-labeled glucose indicated thatS. stenostreptadegraded glucose via the Embden-Meyerhof pathway. The spirochete utilized a clostridial-type clastic reaction to metabolize pyruvate to acetyl-coenzyme A, CO2, and H2, without production of formate. Acetyl-coenzyme A was converted to ethyl alcohol by nicotinamide adenine dinucleotide-dependent acetaldehyde and alcohol dehydrogenase activities. Phosphotransacetylase and acetate kinase catalyzed the formation of acetate from acetyl-coenzyme A. Hydrogenase and lactate dehydrogenase activities were detected in cell extracts. A rubredoxin was isolated from cell extracts ofS. stenostrepta. Preparations of this rubredoxin stimulated acetyl phosphate formation from pyruvate by diethylaminoethyl cellulose-treated extracts ofS. stenostrepta, an indication that rubredoxin may participate in pyruvate cleavage by this spirochete. Nutritional studies showed thatS. stenostreptafermented a variety of carbohydrates, but did not ferment amino acids or other organic acids. An unidentified growth factor present in yeast extract was required by the organism. Exogenous supplements of biotin, riboflavin, and vitamin B12were either stimulatory or required for growth.