A novel obligately anaerobic, proteolytic bacterium, designated AP15T, was isolated from lake sediments of Schirmacher Oasis, Antarctica. The bacterium produced maximum cell mass between 5 and 10 °C in an anaerobic basal medium containing 0·5 % tryptone and peptone. The strain grew optimally at a pH around 8·0 and tolerated NaCl up to a concentration of 7·5 %. It contained diphosphatidylglycerol as the major phospholipid and C15 : 0, C16 : 0 and C17 : 0 as the major cellular fatty acids. Several amino acids, including arginine, leucine, isoleucine, cysteine, glutamate and serine, supported growth. Glutamate was degraded to acetate, propionate, CO2 and H2. In addition, the strain degraded carbohydrates including glucose, raffinose, adonitol, ribose and rhamnose. The main fermentation products during growth on glucose were H2, CO2, formate, acetate, propionate and isovalerate. The DNA G+C content of the bacterium was 24 mol%. On the basis of a phylogenetic analysis, strain AP15T is identified as a close relative of Clostridium subterminale ATCC 25774T, with which it shares 99·5 % similarity at the 16S rRNA gene sequence level; however, it exhibits a low DNA–DNA binding value (55 %) to this strain at the whole-genome level. In addition to showing other major differences with respect to C. subterminale and other members of the genus Clostridium, AP15T also exhibits phenotypic differences. On the basis of these differences, strain AP15T is identified as representing a novel species of the genus Clostridium, for which the name Clostridium schirmacherense sp. nov. is proposed. The type strain is AP15T (=DSM 17394T=JCM 13289T).
Halanaeroarchaeum sulfurireducens gen. nov., sp. nov., the first obligately anaerobic sulfur-respiring haloarchaeon, isolated from a hypersaline lake
