Fig. 2.
Comparison of carbon monoxide dehydrogenase activity of Mycobacterium smegmatis wild-type and ΔcoxL cultures. a Zymographic observation of CO dehydrogenase activity and localization. The upper gel shows enzyme activity stained with the artificial electron acceptor nitroblue tetrazolium chloride in a CO-rich atmosphere. The lower gel shows protein ladder and whole protein stained with Coomassie Blue. Results are shown for whole-cell lysates (L), cytosolic fractions (C), and membrane fractions (M) of wild-type (WT) and ΔcoxL cultures. b Gas chromatography measurement of CO oxidation to sub-atmospheric levels. Mixing ratios are displayed on a logarithmic scale, the dotted line shows the average atmospheric mixing ratios of CO (90 ppbv), and error bars show standard deviations of three biological replicates. c Apparent kinetic parameters of CO oxidation by wild-type cultures. Curves of best fit and kinetic parameters were calculated based on a Michaelis–Menten non-linear regression model. Vmax app and Km app values derived from other models are shown in Table S4. d Examples of traces from oxygen electrode measurements. O2 levels were measured before and after CO addition in both a wild-type and ΔcoxL background. e Summary of rates of O2 consumption measured using an oxygen electrode. Center values show means and error bars show standard deviations from three biological replicates. For all values with different letters, the difference between means is statistically significant (p < 0.001) based on Student’s t-tests