| Abstract: | E. coli K10 was found to grow anaerobically on molecular hydrogen by reducing nitrate, fumarate, and trimethylamine N-oxide when peptone was added to the culture medium. Molar growth yields based on consumed hydrogen estimated from the amounts of reduction products were all 7.8 g cells/mol, suggesting that 1 mol of ATP was produced in the oxidation of 1 mol of hydrogen. Hydrogenase activity measured in terms of hydrogen evolution was several times higher in cells grown on glucose than in cells grown on hydrogen in the presence of fumarate and trimethylamine N-oxide, while hydrogenase activity measured in terms of hydrogen uptake was unchanged in both cases. The ratio of hydrogenase activities measured in terms of hydrogen uptake and evolution was also high in the extract and centrifugal fractions from cells grown in hydrogen. The soluble fraction and trypsin digest of the precipitate at 100,000 X g were subjected to polyacrylamide disc gel electrophoresis and hydrogenase bands were stained by reduction of benzyl viologen with hydrogen and by oxidation of reduced methyl viologen. The resulting patterns suggest that multiple forms of hydrogenase are present and that the amounts of forms functioning in hydrogen evolution were greatly decresed in cells grown on hydrogen in the presence of acceptors. |
