Nitrosophilus kaiyonis sp. nov., a hydrogen-, sulfur- and thiosulfate-oxidizing chemolithoautotroph within “Campylobacteria” isolated from a deep-sea hydrothermal vent in the Mid-Okinawa Trough

A novel bacterium, strain MOT50T, was isolated from the chimney structure at the Iheya North field in the Mid-Okinawa Trough. The cells were motile short rods with a single polar flagellum. Growth was observed between 40 and 65 ℃ (optimum, 52 ℃), at pH values between 5.0 and 7.1 (optimum, pH 6.1) and in the presence of 2.0–4.0% NaCl (optimum, 2.5%). The isolates utilized molecular hydrogen, thiosulfate, or elemental sulfur as the sole electron donor. Thiosulfate, elemental sulfur, nitrate, and molecular oxygen are utilized as the sole electron acceptor. Ammonium is required as a nitrogen source. Thiosulfate, elemental sulfur, sulfate, or sulfite serves as a sulfur source for growth. The G + C content of the genomic DNA was 28.9%. Phylogenetic analysis based on the 16S rRNA gene sequences indicated that strain MOT50T belonged to the genus Nitrosophilus of the class “Campylobacteria”, and its closest relative was Nitrosophilus labii HRV44T (97.20%). On the basis of the phylogenetic, physiological, and molecular characteristics, it is proposed that the organism represents a novel species within the genus Nitrosophilus, Nitrosophilus kaiyonis sp. nov. The type strain is MOT50T (= JCM 39187T = KCTC 25251T).