Clostridium schirmacherense sp. nov., an obligately anaerobic, proteolytic, psychrophilic bacterium isolated from lake sediment of Schirmacher Oasis, Antarctica

Abstract

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 : 0and C17 : 0as the major cellular fatty acids. Several amino acids, including arginine, leucine, isoleucine, cysteine, glutamate and serine, supported growth. Glutamate was degraded to acetate, propionate, CO2and 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 AP15Tis identified as a close relative ofClostridium subterminaleATCC 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 toC. subterminaleand other members of the genusClostridium, AP15Talso exhibits phenotypic differences. On the basis of these differences, strain AP15Tis identified as representing a novel species of the genusClostridium, for which the nameClostridium schirmacherensesp. nov. is proposed. The type strain is AP15T(=DSM 17394T=JCM 13289T).