Thermococcus camini sp. nov., a hyperthermophilic and piezophilic archaeon isolated from a deep-sea hydrothermal vent at the Mid-Atlantic Ridge

Abstract

A coccoid-shaped, strictly anaerobic, hyperthermophilic and piezophilic organoheterotrophic archaeon, strain Iri35cT, was isolated from a hydrothermal chimney rock sample collected at a depth of 2300 m at the Mid-Atlantic Ridge (Rainbow vent field). Cells of strain Iri35cT grew at NaCl concentrations ranging from 1–5 % (w/v) (optimum 2.0 %), from pH 5.0 to 9.0 (optimum 7.0–7.5), at temperatures between 50 and 90 °C (optimum 75–80 °C) and at pressures from 0.1 to at least 50 MPa (optimum: 10–30 MPa). The novel isolate grew on complex organic substrates, such as yeast extract, tryptone, peptone or beef extract, preferentially in the presence of elemental sulphur or l-cystine; however, these molecules were not necessary for growth. Its genomic DNA G+C content was 54.63 mol%. The genome has been annotated and the metabolic predictions are in accordance with the metabolic characteristics of the strain and of Thermococcales in general. Phylogenetic analyses based on 16S rRNA gene sequences and concatenated ribosomal protein sequences showed that strain Iri35cT belongs to the genus Thermococcus, and is closer to the species T. celericrescens and T. siculi . Average nucleotide identity scores and in silico DNA–DNA hybridization values between the genome of strain Iri35cT and the genomes of the type species of the genus Thermococcus were below the species delineation threshold. Therefore, and considering the phenotypic data presented, strain Iri35cT is suggested to represent a novel species, for which the name Thermococcus camini sp. nov. is proposed, with the type strain Iri35cT (=UBOCC M-2026T=DSM 111003T).