Thermaerobacter composti sp nov., a novel extremely thermophilic bacterium isolated from compost

A novel extremely thermophilic bacterium (Ni80(T)) was isolated from food sludge compost in Japan. Cells were Gram-positive, spore-forming, strictly-aerobic and rod-shaped with peritrichous flagella. The novel isolate grew at pH 6.5-10.5 but not at pH 11.0 (optimum pH 8.0) and 52-79 degrees C but not 80 degrees C (optimum 70 degrees C). The strain could not grow in more than 1% NaCl. The G + C content of the genomic DNA is 72 mol%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain Ni80(T) belonged to the genus Thermaerobacter, and that the strain was most closely related to Thermaerobacter subterraneus ATCC BAA-137(T) (98.2%), Thermaerobacter nagasakiensis JCM 11223(T) (98.2%), Thermaerobacter marianensis JCM 10246(T) (98.0%) and Thermaerobacter litoralis JCM 13210(T) (97.7%). DNA-DNA hybridization showed relatedness values of less than 10% with these species. On the basis of phenotypic and molecular data, strain Ni80(T) represent a novel species of the genus Thermaerobacter, for which the name Thermaerobacter composti sp. nov. is proposed. The type strain is Ni80(T) (=JCM 15650(T) =ATCC BAA-1731(T)).