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

A novel moderately thermophilic, microaerobic to anaerobic, chemolithoautotrophic bacterium, designated strain CRT, was isolated from a deep-sea hydrothermal vent site at 36 degrees N on the Mid-Atlantic Ridge. Cells were Gram-negative, non-motile rods. The organism grew at 45-65 degrees C and pH 6.5-7.4, with optimum growth at 55 degrees C and pH 6.9-7.1. The NaCl range for growth was 5-50 g l(-1) (optimum 30 g l(-1)). Strain CRT was an obligate chemolithoautotroph, growing with H2 as energy source, sulfur, nitrate or oxygen as electron acceptors and CO2 as 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 to Caminibacter hydrogeniphilus (94.9% similarity). On the basis of phenotypic and phylogenetic data, it is proposed that the isolate represents a novel species, Caminibacter profundus sp. 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 genera Nautilia and Caminibacter and other members of the class 'Epsilonproteobacteria'. The lineage encompassing the genera Nautilia and Caminibacter is therefore proposed as a new order, Nautiliales ord. nov., represented by a single family, Nautiliaceae fam. nov.