Brevibacillus nitrificans sp. nov., a nitrifying bacterium isolated from a microbiological agent for enhancing microbial digestion in sewage treatment tanks

A heterotrophic nitrifying bacterium, designated strain DA2(T), was isolated from a microbiological agent for enhancing microbial digestion in sewage treatment tanks. Cells of strain DA2(T) were Gram-positive, facultatively anaerobic, sporulating rods that were motile by means of peritrichous flagella; they were able to grow at pH 5-8. The major isoprenoid quinone of strain DA2(T) was menaquinone-7 (MK-7) and its cellular fatty acid profile consisted mainly of iso-C(15 : 0) (18.6 %) and anteiso-C(15 : 0) (69.1 %). The DNA G+C content was 54.1 mol%. 16S rRNA gene sequence phylogeny suggested that strain DA2(T) is a member of the genus Brevibacillus, with highest sequence similarities (in parentheses) to the type strains of Brevibacillus choshinensis (99.7 %), B. formosus (99.4 %), B. brevis (99.4 %), B. agri (99.0 %), B. reuszeri (98.8 %), B. parabrevis (98.7 %), B. centrosporus (98.6 %), B. limnophilus (97.4 %), B. panacihumi (97.3 %) and B. invocatus (97.3 %). DNA-DNA hybridization showed less than 60 % relatedness between strain DA2(T) and type strains of the most closely related species given above. Given the significant differences in phenotypic and chemotaxonomic characteristics, and phylogenetic analysis based on the 16S rRNA sequence and DNA-DNA relatedness data, the isolate merits classification as a novel species, for which the name Brevibacillus nitrificans is proposed; the type strain of this species is DA2(T) (= JCM 15774(T) = NCIMB 14531(T)).