Caldithrix palaeochoryensis sp. nov., a thermophilic, anaerobic, chemo-organotrophic bacterium from a geothermally heated sediment, and emended description of the genus Caldithrix

Abstract

A novel thermophilic, strictly anaerobic, chemo-organotrophic bacterium, designated MC^T, was isolated from a geothermally heated sediment of a marine hydrothermal system at Palaeochory Bay, Milos, Greece. Cells of strain MC^Twere rods of variable length (4–12 μm) and width (0.2–0.3 μm), occurring as single cells or forming large aggregates that were visible as flocs. Strain MC^Tgrew optimally at pH 7.0 and 60 °C and with 3 % (w/v) NaCl. Strain MC^Tgrew chemo-organoheterotrophically and fermented peptides and di- and polysaccharides in the presence of 0.1 g yeast extract l⁻¹. The DNA G+C content of strain MC^Twas 43.3 mol%. Phylogenetic analysis of the 16S rRNA gene sequence placed strain MC^Twithin the genusCaldithrix. However, strain MC^Tpossessed certain phenotypic features that differentiated it from the type strain of the only species of the genusCaldithrixdescribed to date. On the basis of phylogenetic and phenotypic characteristics, it is proposed that strain MC^Trepresents a novel species,Caldithrix palaeochoryensissp. nov. The type strain is MC^T(=DSM 21940^T=VKM B-2536^T). In addition, an emended description of the genusCaldithrixis presented.