Simultaneous sulfide and methane oxidation by an extremophile

Hydrogen sulfide (H(2)S) and methane (CH(4)) are produced in anoxic environments through sulfate reduction and organic matter decomposition. Both gases diffuse upwards into oxic zones where aerobic methanotrophs mitigate CH(4) emissions by oxidizing this potent greenhouse gas. Although methanotrophs in myriad environments encounter toxic H(2)S, it is virtually unknown how they are affected. Here, through extensive chemostat culturing we show that a single microorganism can oxidize CH(4) and H(2)S simultaneously at equally high rates. By oxidizing H(2)S to elemental sulfur, the thermoacidophilic methanotroph Methylacidiphilum fumariolicum SolV alleviates the inhibitory effects of H(2)S on methanotrophy. Strain SolV adapts to increasing H(2)S by expressing a sulfide-insensitive ba(3)-type terminal oxidase and grows as chemolithoautotroph using H(2)S as sole energy source. Genomic surveys revealed putative sulfide-oxidizing enzymes in numerous methanotrophs, suggesting that H(2)S oxidation is much more widespread in methanotrophs than previously assumed, enabling them to connect carbon and sulfur cycles in novel ways.