[Hydrogenase activity of the methylotroph, Pseudomonas methylica]

The cells of Pseudomonas methylica, strain 2, cultivated in a medium containing methanol, displayed the activity of hydrogenase in the exchange reaction (D2--H2O) and in the absorption of H2 in the presence of methylviologen, azocarmine, methylene blue, and ferricyanide. The rate of H2 utilization was highest in the presence of methylviologen. Cell extracts absorb H2 in the presence of methylviologen, NAD, and NADP, but much faster in the presence of flavin mononucleotide. The bulk of the hydrogenase remains, during centrifugation of the initial cell extract (3,000 g), in the soluble fraction (144,000 g). The absorption of oxygen by the cell suspensions and the incorporation of 14C of formiate into the cells are stimulated by H2. The cells, however, cannot grow in the autotrophic conditions at the account of molecular hydrogen and CO2.