Clostridium lactatifermen tans sp. nov., a lactate-fermenting anaerobe isolated from the caeca of a chicken.

An obligately anaerobic, lactate-fermenting bacterium (strain G17T) was isolated from the caeca of a 31-day-old chicken. Grown at neutral pH, cells were rod-shaped with tapered ends and showed no motility and no spore formation. Electron microscopy showed that the cell walls had a gram-positive structure. The DNA G+C content was 44.6 mol %. Based on 16S rDNA sequence analysis, strain G17T was considered to belong to the low-G+C-content gram-positive bacteria of cluster XIV subgroup b and most closely related to Clostridium propionicum (93.5%) and Clostridium neopropionicum (93.5%). The optimum temperature for growth was 41 degrees C and the optimum pH was pH 6.4-7.3. The optimum temperature of 41 degrees C suggests that strain G17T might have become adapted to the body temperature of chickens. Strain G17T was able to grow on a variety of organic compounds. Most of these compounds were converted to acetate, propionate and traces of butyrate and isovalerate. In media with mixtures of substrates, lactate was degraded by strain G17T before the other substrates. This indicates that strain G17T might be important in the fermentation of lactate in the caeca of chickens. Based on its physiological and phylogenetic characteristics, it is proposed that strain G17T should be assigned to the genus Clostridium as a novel species, Clostridium lactatifermentans sp. nov.