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 t he 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, a nd at an NaCl concentration of < 0.5% (w/v). It survived freeze-thawin g 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 su bstrates, only xylan supported growth. The organism also grew on a var iety of mono- and disaccharides including the cyanobacterial cell wall constituent, N-acetyl glucosamine. Fermentation products on a mol pro duct per 100 mol of hexose monomer fermented basis were: acetate, 72 f ormate, 72; butyrate, 55; hydrogen, 114; and CO2, 100. Not detectable in the culture medium (< 2 mol per 100 mol of monomer) were lactate, p ropionate, ethanol, il-propanol, n-butanol, and succinate. The G+C con tent of the DNA from the bacterium was 33 mol%, and a phylogenetic ana lysis indicated that it grouped closely with members of the RNA-DNA ho mology group I of the genus Clostridium. It differed from other specie s of this genus with regard to growth temperature optimum, substrate r ange, and fermentation pattern, and is therefore designated as a new s pecies of Clostridium for which the name Clostridium vincentii is prop osed. The type strain is lac-1 (DSM 10228).