Caminibacter profundus sp. nov., a novel thermophile of Nautiliales ord. nov. within the class ‘Epsilonproteobacteria’, isolated from a deep-sea hydrothermal vent

Abstract

A novel moderately thermophilic, microaerobic to anaerobic, chemolithoautotrophic bacterium, designated strain CRT, was isolated from a deep-sea hydrothermal vent site at 36°N on the Mid-Atlantic Ridge. Cells were Gram-negative, non-motile rods. The organism grew at 45–65 °C and pH 6·5–7·4, with optimum growth at 55 °C and pH 6·9–7·1. The NaCl range for growth was 5–50 g l−1(optimum 30 g l−1). Strain CRTwas an obligate chemolithoautotroph, growing with H2as energy source, sulfur, nitrate or oxygen as electron acceptors and CO2as carbon source. Hydrogen sulfide and ammonium were the respective products of sulfur and nitrate reduction. The G+C content of the genomic DNA was 32·1 mol%. Based on 16S rRNA gene sequence analysis, this organism was most closely related toCaminibacter hydrogeniphilus(94·9 % similarity). On the basis of phenotypic and phylogenetic data, it is proposed that the isolate represents a novel species,Caminibacter profundussp. nov. The type strain is CRT(=DSM 15016T=JCM 11957T). The phylogenetic data also correlate well with the significant phenotypic differences between the lineage encompassing the generaNautiliaandCaminibacterand other members of the class ‘Epsilonproteobacteria’. The lineage encompassing the generaNautiliaandCaminibacteris therefore proposed as a new order,Nautilialesord. nov., represented by a single family,Nautiliaceaefam. nov.