Anaerobranca gottschalkii sp. nov., a novel thermoalkaliphilic bacterium that grows anaerobically at high pH and temperature.

A novel thermoalkaliphilic, obligately anaerobic bacterium was isolated from a humid soil sample of a hot inlet of Lake Bogoria, Kenya. The newly isolated strain grows optimally at pH 9.5 and 50-55 degrees C and its growth range is pH 6.0-10.5 and 30-65 degrees C. Unlike the already known thermoalkaliphiles, the strain grows heterotrophically on a variety of mono- and polysaccharides (glucose, ribose, mannose, fructose, sucrose, maltose, starch, pullulan, xylan and cellulose) and on proteinaceous substrates such as yeast extract, peptone and tryptone. No dissimilatory sulfate reduction was observed, whereas thiosulfate was found to enhance growth when glucose or starch were used as substrates. Under optimal conditions, the doubling time is 48 min. Sodium ions are necessary for growth, with an optimal concentration of 230 mM (1% NaCl, w/v) at pH 9.5. The rod-shaped cells are motile in the exponential growth phase under optimal growth conditions. Despite the Gram-negative staining and negative KOH assay, the strain is a Gram-positive organism, having an atypically thin cell wall. A sheath-like structure occurs at the cell separation area and parts of a surface layer-like structure were also observed. Based on physiological properties and molecular biological analysis, the strain falls within the radiation of the clostridia and represents a new species of Anaerobranca within the Clostridium/Bacillus subphylum of the Gram-positive bacteria. Strain LBS3T (= DSM 13577T) is named Anaerobranca gottschalkii sp. nov. and is designated as the type strain.