A bacterial isolate from the Black Sea oxidizes sulfide with manganese(IV) oxide.

Mn is one of the most abundant redox-sensitive metals on earth. Some microorganisms are known to use Mn(IV) oxide (MnO) as electron acceptor for the oxidation of organic compounds or hydrogen (H), but so far the use of sulfide (HS) has been suggested but not proven. Here we report on a bacterial isolate which grows autotrophically and couples the reduction of MnO to the oxidation of HS or thiosulfate (SO) for energy generation. The isolate, originating from the Black Sea, is a species within the genus , which typically occurs with high cell numbers in the vicinity of sulfidic environments [Y. Han, M. Perner, 6, 989 (2015)]. HS and SO are oxidized completely to sulfate (SO) without the accumulation of intermediates. In the culture, Mn(IV) reduction proceeds via Mn(III) and finally precipitation of Ca-rich Mn(II) carbonate [Mn(Ca)CO]. In contrast to Mn-reducing bacteria, which use organic electron donors or H, Fe oxides are not observed to support growth, which may either indicate an incomplete gene set or a different pathway for extracellular electron transfer.