Hydrogen-mediated mannose uptake in Azotobacter vinelandii.

Azotobacter vinelandii can grow mixotrophically with H2 plus mannose under N2-fixing conditions (T. Y. Wong and R. J. Maier, J. Bacteriol. 163:528-533, 1985). Mixotrophically grown cultures incubated in H2 transported mannose with a Vmax fourfold greater than that observed for cultures incubated in argon, but H2 did not change the apparent Km for mannose. Respiratory inhibitors, such as potassium cyanide, hydroxylamine, and p-chloromercuribenzoic acid, as well as the proton conductor carbonyl cyanide m-chlorophenyl-hydrazone inhibited mannose uptake. We suggest that one of the roles of H2 in mixotrophic metabolism is to supply energy that facilitates mannose transport.