A gram-positive, motile, strict anaerobic spore-forming bacterium was isolated from the over-cooled brine in the permafrost. The optimal temperature for isolate growth was 5-6 degrees C at pH 6.8-7.2. The bacterium was growing on the medium rich in saccharides and disaccharides. Out of polysaccharides tested, only xylan sustained the growth. Fermentation of the hexoses led to the formation of acetate, butyrate, lactate, H2,CO2 and some formate and ethanol. Cell wall peptidoglycan contained meso-diaminopimelic acid. The major fatty acids of the cell wall were C(14:0) and C(16:1c9). The content of G-C pairs in DNA was 31.4 mol%. As phylogenetic analysis has shown, it is closely linked to the members of cluster 1 of Clostridium. It differs from the other species of the genus by the substrates necessary for the growth, products forming as a result of the fermentation and content of the fatty acids in the cell wall. Thus, it was suggested to describe this strain as a new species named Clostridium algoriphilum. Type strain 14D1 was deposited into the Russian Collection of the Microorganisms VKM B-2271T and German Collection of the Microorganisms DSM 16153T .