Abstract
Cell suspensions of uptake-hydrogenase-deficient (hup-) mutants of a wild-type (B10S) and a nifHDK deletion strain of Rhodobacter capsulatus were used comparatively to characterize the conventional, Mo-containing and the alternative, “iron-only” nitrogenase of this organism by determining the H2 production and acetylene reduction activities under argon and dinitrogen atmospheres. A comparison with the corresponding hup+ strains revealed that the hup- mutation did not affect the nitrogenase activity and specificity within the acetylene-reduction assay, but caused a significant increase in H2 production, which was more prominent in the case of the ΔnifHDK strain. The ΔnifHDK hup- cells, grown in Mo-depleted medium and, thus, expressing the alternative nitrogenase system, were more than ten times less active in the acetylene-reduction assay but exhibited H2 production rates equivalent to about 60% of the rates obtained with B10S hup- cells after growth in a medium containing 10 μM MoO-4. When these conditions were applied, the B10S strain only expressed the Mo nitrogenase. Under an argon atmosphere containing about 5.5% (v/v) acetylene and under a dinitrogen atmosphere, ΔnifHDK hup- cells produced H2 at even higher rates than B10S hup- cells. The implications of our findings on a possible biotechnological H2 production and on the mechanism of nitrogenase catalysis are considered.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call