Fig. 3.
Hydrogenase activity in carbon-limited stationary-phase cultures of P. methylaliphatogenes strain K22T. (A) Density-dependent whole-cell oxidation of H2. (B) Whole-cell oxidation of H2 following nitrogen-sparging (anoxic), cyanide-treatment, or heat-killing of the cells. For both A and B, H2 concentration was measured using a H2 microsensor. Positive values infer net H2 evolution, whereas negative values infer net H2 oxidation. Error bars represent SDs from three biological replicates; *P < 0.05, **P < 0.01, ***P < 0.001 (Student’s t test). (C) Zymographic detection of hydrogenase activity in concentration-normalized cell lysates (L), cytosols (C), and membranes (M) separated by native PAGE and anaerobically stained with the artificial electron acceptor nitroblue tetrazolium. Acidobacterial samples (labeled acido in subscript) were run against the M. smegmatis mc2155 as a positive control (+ve) and its hydrogenase triple mutant derivative as a negative control (−ve).