Effect of Hydrogen, Sucrose and Oxygen on Uptake Hydrogenase in Nitrogen-fixing and Ammonium-grown Pseudomonas saccharophila ATCC 15946

Abstract

SUMMARY: Pseudomonas saccharophila, grown microaerobically in batch culture, showed much higher uptake hydrogenase activity in N2-fixing than in NH+4-grown cultures. Hydrogenase synthesis was induced by H2 under a low partial pressure of O2 and under air, in autotrophic as well as in heterotrophic conditions, provided that the sucrose concentration was relatively low. Sucrose at 15 mM repressed hydrogenase formation but did not inhibit preformed activity. Other utilizable carbon substrates repressed, while non-utilizable substrates did not repress, hydrogenase synthesis. The activity, unlike nitrogenase, was not sensitive to O2 but hydrogenase synthesis was partially repressed by O2.