Thermobacillus composti sp. nov., a moderately thermophilic bacterium isolated from a composting reactor.

A Gram-negative, rod-shaped, spore-forming and moderately thermophilic bacterium, strain KWC4(T), was isolated from a composting reactor. Cells of strain KWC4(T) were 2.0-5.0 microm long and 0.5-0.7 microm in diameter. Strain KWC4(T) grew aerobically at 32-61 degrees C, with optimal growth occurring at 50 degrees C. It grew at pH 5.6-10.1, with optimal growth at around pH 9.0. The optimum NaCl concentration for growth was almost 0 % (w/v), but strain KWC4(T) was moderately halotolerant and was able to grow at NaCl concentrations up to 4.4 % (w/v). The DNA G+C content of strain KWC4(T) was 60.0 mol%. The major fatty acids were iso-16 : 0 (39.0 %) and anteiso-15 : 0 (33.3 %). Based on 16S rRNA gene sequence similarity data, strain KWC4(T) belonged to the genus Thermobacillus and was related to Thermobacillus xylanilyticus. However, strain KWC4(T) had a 38 bp insertion sequence located near the 3' end of its 16S rRNA gene that was not present in T. xylanilyticus. The 16S rRNA gene sequence similarity value between strain KWC4(T) and T. xylanilyticus was 95.7 %. The DNA-DNA hybridization value between strain KWC4(T) and T. xylanilyticus strain XE(T) was 66 %. On the basis of phenotypic and genotypic evidence, strain KWC4(T) (=DSM 18247(T)=JCM 13945(T)) is the type strain of a novel species, for which the name Thermobacillus composti sp. nov. is proposed.