Organohalide-respiringDesulfolunaspecies isolated from marine environments

AbstractThe genusDesulfolunacomprises two anaerobic sulfate-reducing strains,D. spongiiphilaAA1⊤andD. butyratoxydansMSL71⊤of which only the former was shown to perform organohalide respiration (OHR). Here we isolated a third member of this genus from marine intertidal sediment, designedD. spongiiphilastrain DBB. All threeDesulfolunastrains harbour three reductive dehalogenase gene clusters (rdhABC) and corrinoid biosynthesis genes in their genomes. Brominated but not chlorinated aromatic compounds were dehalogenated by all three strains. TheDesulfolunastrains maintained OHR in the presence of 20 mM sulfate or 20 mM sulfide, which often negatively affect OHR. Strain DBB sustained OHR with 2% oxygen in the gas phase, in line with its genetic potential for reactive oxygen species detoxification. Reverse transcription-quantitative PCR (RT-qPCR) revealed differential induction ofrdhAgenes in strain DBB in response to 1,4-dibromobenzene or 2,6-dibromophenol. Proteomic analysis confirmed differential expression ofrdhA1with 1,4-dibromobenzene, and revealed a possible electron transport chain from lactate dehydrogenases and pyruvate oxidoreductase to RdhA1 via menaquinones and either RdhC, or Fix complex (electron transfer flavoproteins), or Qrc complex (Type-1 cytochrome c3:menaquinone oxidoreductase).