An anaerobic, psychrophilic bacterium, strain MO-SPC2T, was isolated from a methanogenic microbial community in a continuous-flow bioreactor that was established from subseafloor sediments collected from off the Shimokita Peninsula of Japan in the north-western Pacific Ocean. Cells were pleomorphic: spherical, annular, curved rod, helical and coccoid cell morphologies were observed. Motility only occurred in helical cells. Strain MO-SPC2T grew at 0–17 °C (optimally at 9 °C), at pH 6.0–8.0 (optimally at pH 6.8–7.2) and in 20–40 g NaCl l−1 (optimally at 20–30 NaCl l−1). The strain grew chemo-organotrophically with mono-, di- and polysaccharides. The major end products of glucose fermentation were acetate, ethanol, hydrogen and carbon dioxide. The abundant polar lipids of strain MO-SPC2T were phosphatidylglycolipids, phospholipids and glycolipids. The major cellular fatty acids were C14 : 0, C16 : 0 and C16 : 1ω9. Isoprenoid quinones were not detected. The G+C content of the DNA was 32.3 mol%. 16S rRNA gene-based phylogenetic analysis showed that strain MO-SPC2T was affiliated with the genus
Sphaerochaeta
within the phylum
Spirochaetes
, and its closest relatives were
Sphaerochaeta pleomorpha
GrapesT (88.4 % sequence identity),
Sphaerochaeta globosa
BuddyT (86.7 %) and
Sphaerochaeta coccoides
SPN1T (85.4 %). Based on phenotypic characteristics and phylogenetic traits, strain MO-SPC2T is considered to represent a novel species of the genus
Sphaerochaeta
, for which the name Sphaerochaeta multiformis sp. nov. is proposed. The type strain is MO-SPC2T ( = JCM 17281T = DSM 23952T). An emended description of the genus
Sphaerochaeta
is also proposed.
Sphaerochaeta multiformis sp. nov., an anaerobic, psychrophilic bacterium isolated from subseafloor sediment, and emended description of the genus Sphaerochaeta
