Uptake of carbon monoxide and hydrogen at environmentally relevant concentrations by mycobacteria

Liquid culture assays revealed a previously unreported capacity for Mycobacterium bovis BCG, M. gordonae, and M. marinum to oxidize CO and for M. smegmatis to consume molecular hydrogen. M. bovis BCG, M. gordonae, M. smegmatis, and M. tuberculosis H37Ra oxidized CO at environmentally relevant concentrations (<50 ppm); H-2 oxidation by M. gordonae and M. smegmatis also occurred at environmentally relevant concentrations (< 10 ppm). CO was not consumed by M. avium or M. microti, although the latter appeared to possess CO dehydrogenase (CODH) genes based on PCR results with primers designed for the CODH large subunit, coxL. M. smegmatis and M. gordonae oxidized CO under suboxic (10 and 1% atmospheric oxygen) and anoxic conditions in the presence of nitrate; no oxidation occurred under anoxic conditions without nitrate. Similar results were obtained for H, oxidation by M. smegmatis. Phylogenetic analyses of coxL PCR products indicated that mycobacterial sequences form a subclade distinct from that of other bacterial coxL, with limited differentiation among fast- and slow-growing strains.