PSYCHROMONAS-ANTARCTICUS GEN. NOV., SP. NOV., A NEW AEROTOLERANT ANAEROBIC, HALOPHILIC PSYCHROPHILE ISOLATED FROM POND SEDIMENT OF THE MCMURDO ICE SHELF, ANTARCTICA

A gram-negative, rod-to oval-shaped, aerotolerant anaerobic bacterium was isolated from an anaerobic enrichment inoculated with sediment tak en from below the cyanobacterial mat of a high-salinity pond near Brat ina Island on the McMurdo Ice Shelf, Antarctica. The organism was posi tive for terminal oxidase and catalase and was motile by means of a po lar flagellum. Optimal growth of anaerobic cultures occurred at 12 deg rees C, at pH 6.5, and at an NaCl concentration of 3% (w/v). Of a vari ety of polysaccharides tested, only starch and glycogen supported grow th. No growth was observed on cellulosic substrates and xylan, and the organism was unable to attack esculin. Monosaccharides and disacchari des, including the cyanobacterial cell-wall constituent N-acetyl gluco samine, were fermented. Per 100 mol of hexose, the following products (in mol) were formed: acetate, 60; formate, 130; ethanol, 56; lactate, 73; CO2, 15; and butyrate, 2. Propionate, ethanol, n-propanol, n-buta nol and succinate were not detectable in the culture medium (< 1 mol p er 100 mol of monomer). Hydrogen was not detected in the head space (d etection limit < 10(-5) atm). Growth yields in aerobic static liquid c ultures were slightly higher than those in anaerobic culture, and ferm entation favoured acetate at the expense of electron sink products. Gr owth was inhibited in aerobic shaking cultures, and the organism did n ot utilize nitrate or sulfate as electron accepters. The G+C content o f the DNA from the bacterium was 42.8 mol%. A phylogenetic analysis in dicated that the organism is a member of the gamma-subgroup of Proteob acteria, but that it is distinct from other members of this group base d on the sequence of its 16S rRNA gene, mol% G+C, morphology, and phys iological and biochemical characteristics. It is designated as a new g enus and species; the type strain is star-1 (DSM 10704).