Fig. 2
Hydrogenase and carbon monoxide dehydrogenase activity of Thermomicrobium roseum cultures during nutrient limitation. a, b Oxidation of molecular hydrogen (H2; a) and carbon monoxide (CO; b) to sub-atmospheric levels by T. roseum cultures. Error bars show standard deviations of three biological replicates, with heat-killed cells monitored as a negative control (grey dashed lines). Mixing ratios of H2 and CO are displayed on a logarithmic scale and dotted lines show the average atmospheric mixing ratios of H2 (0.53 ppmv) and CO (0.10 ppmv). c, d Apparent kinetic parameters of H2 (c) and CO (d) oxidation by T. roseum whole cells. Curves of best fit and kinetic parameters were calculated based on a Michaelis–Menten non-linear regression model. Values calculated based on Lineweaver-Burk, Hanes-Woolf, and Eadie-Hofstee plots are shown in Table S2. e Zymographic observation of hydrogenase and carbon monoxide dehydrogenase activity in T. roseum whole-cell lysates. The first two lanes show protein ladder and whole protein stained with Coomassie Blue. The third and fourth lanes show hydrogenase and carbon monoxide dehydrogenase activity stained with the artificial electron acceptor nitroblue tetrazolium in a H2-rich and CO-rich atmosphere respectively. f Amperometric measurements of hydrogenase activity in T. roseum whole cells. The rate of H2 oxidation was measured with a hydrogen electrode before and after treatment with the respiratory uncouplers and ionophores carbonyl cyanide m-chlorophenyl hydrazine (CCCP), nigericin, and valinomycin
