Rhabdothermus arcticus gen. nov., sp. nov., a member of the family Thermaceae isolated from a hydrothermal vent chimney in the Soria Moria vent field on the Arctic Mid-Ocean Ridge

Abstract

A novel thermophilic member of the family Thermaceae, designated strain 2M70-1(T), was isolated from the wall of an active white smoker chimney collected in the Soria Moria vent field at 71 °N in the Norwegian-Greenland Sea. Cells of the strain were Gram-negative, non-motile rods. Growth was observed at 37-75 °C (optimum 65 °C), at pH 6-8 (optimum pH 7.3) and in 1-5 % (w/v) NaCl (optimum 2.5-3.5 %). The isolate was aerobic but could also grow anaerobically using nitrate or elemental sulfur as electron acceptors. The strain was obligately heterotrophic, growing on complex organic substrates like yeast extract, Casamino acids, tryptone and peptone. Pyruvate, acetate, butyrate, sucrose, rhamnose and maltodextrin were used as complementary substrates. The G+C content of the genomic DNA was 68 mol%. Cells possessed characteristic phospholipids and glycolipids. Major fatty acids constituted saturated and unsaturated iso-branched and saturated anteiso-branched forms. Menaquinone 8 was the sole respiratory lipoquinone. Phylogenetic analysis of 16S rRNA gene sequences placed the strain in the family Thermaceae in the phylum 'Deinococcus-Thermus', which is consistent with the chemotaxonomic data. On the basis of phenotypic and phylogenetic data, strain 2M70-1(T) ( = JCM 15963(T) = DSM 22268(T)) represents the type strain of a novel species of a novel genus, for which the name Rhabdothermus arcticus gen. nov., sp. nov. is proposed.