Clostridium vincentii sp nov, a new obligately anaerobic, saccharolytic, psychrophilic bacterium isolated from low-salinity pond sediment of the McMurdo Ice Shelf, Antarctica

A gram-positive, motile, rod-shaped, strictly anaerobic bacterium was isolated from an enrichment initiated with sediment taken from below the cyanobacterial mat of a low-salinity pond on the McMurdo Ice Shelf, Antarctica. The organism grew optimally at 12 degrees C, at pH 6.5, and at an NaCl concentration of < 0.5% (w/v). It survived freeze-thawing at low salt concentrations, but not exposure to temperatures over 25 degrees C for more than 20 h or short-term exposure to temperatures > 50 degrees C. Out of a variety of polysaccharides tested as growth substrates, only xylan supported growth. The organism also grew on a variety of mono- and disaccharides including the cyanobacterial cell wall constituent, N-acetyl glucosamine. Fermentation products on a mol product per 100 mol of hexose monomer fermented basis were: acetate, 72 formate, 72; butyrate, 55; hydrogen, 114; and CO2, 100. Not detectable in the culture medium (< 2 mol per 100 mol of monomer) were lactate, propionate, ethanol, il-propanol, n-butanol, and succinate. The G+C content of the DNA from the bacterium was 33 mol%, and a phylogenetic analysis indicated that it grouped closely with members of the RNA-DNA homology group I of the genus Clostridium. It differed from other species of this genus with regard to growth temperature optimum, substrate range, and fermentation pattern, and is therefore designated as a new species of Clostridium for which the name Clostridium vincentii is proposed. The type strain is lac-1 (DSM 10228).