Sulfurihydrogenibium azorense, sp. nov., a thermophilic hydrogen-oxidizing microaerophile from terrestrial hot springs in the Azores

Abstract

Five hydrogen-oxidizing, thermophilic, strictly chemolithoautotrophic, microaerophilic strains, with similar (99–100 %) 16S rRNA gene sequences were isolated from terrestrial hot springs at Furnas, São Miguel Island, Azores, Portugal. The strain, designated Az-Fu1T, was characterized. The motile, 0·9–2·0 μm rods were Gram-negative and non-sporulating. The temperature growth range was from 50 to 73 °C (optimum at 68 °C). The strains grew fastest in 0·1 % (w/v) NaCl and at pH 6, although growth was observed from pH 5·5 to 7·0. Az-Fu1Tcan use elemental sulfur, sulfite, thiosulfate, ferrous iron or hydrogen as electron donors, and oxygen (0·2–9·0 %, v/v) as electron acceptor. Az-Fu1Tis also able to grow anaerobically, with elemental sulfur, arsenate and ferric iron as electron acceptors. The Az-Fu1TG+C content was 33·6 mol%. Maximum-likelihood analysis of the 16S rRNA phylogeny placed the isolate in a distinct lineage within theAquificales, closely related toSulfurihydrogenibium subterraneum(2·0 % distant). The 16S rRNA gene of Az-Fu1Tis 7·7 % different from that ofPersephonella marinaand 6·8 % different fromHydrogenothermus marinus. Based on the phenotypic and phylogenetic characteristics presented here, it is proposed that Az-Fu1Tbelongs to the recently described genusSulfurihydrogenibium. It is further proposed that Az-Fu1Trepresents a new species,Sulfurihydrogenibium azorense.