Sphaerochaeta multiformis sp nov.; an anaerobic, psychrophilic bacterium isolated from subseafloor sediment, and emended description of the genus Sphaerochaeta

An anaerobic, psychrophilic bacterium, strain MO-SPC2(T), 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-SPC2(T) grew at 0-17 degrees C (optimally at 9 degrees 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 C-14:0, C-16:0 and C-16:1 omega 9. lsoprenoid quinones were not detected. The G+C content of the DNA was 32.3 molok. 16S rRNA gene-based phylogenetic analysis showed that strain MO-SPC2(T) was affiliated with the genus Sphaerochaeta within the phylum Spirochaetes, and its closest relatives were Sphaerochaeta pleomorpha Grapes(T) (88.4% sequence identity), Sphaerochaeta globosa BuddyT (86.7%) and Sphaerochaeta coccoides SPN1(T) (85.4%). Based on phenotypic characteristics and phylogenetic traits, strain MO-SPC2(T) is considered to represent a novel species of the genus Sphaerocha eta, for which the name Sphaerochaeta multiformis sp. nov. is proposed. The type strain is MO-SPC2T (=JCM 17281(T)= DSM 23952(T)). An emended description of the genus Sphaerochaeta is also proposed.