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 MCT, was isolated from a geothermally heated sediment of a marine hydrothermal system at Palaeochory Bay, Milos, Greece. Cells of strain MCT were rods of variable length (4-12 mm) and width (0.2-0.3 μm), occurring as single cells or forming large aggregates that were visible as flocs. Strain MCT grew optimally at pH 7.0 and 60 °C and with 3% (w/v) NaCl. Strain MCT grew chemoorganoheterotrophically 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 MCT was 43.3 mol%. Phylogenetic analysis of the 16S rRNA gene sequence placed strain MC T within the genus Caldithrix. However, strain MCT possessed certain phenotypic features that differentiated it from the type strain of the only species of the genus Caldithrix described to date. On the basis of phylogenetic and phenotypic characteristics, it is proposed that strain MCT represents a novel species, Caldithrix palaeochoryensis sp. nov. The type strain is MCT (=DSM 21940T =VKM B-2536 T). In addition, an emended description of the genus Caldithrix is presented. © 2010 IUMS.