Neobacillus nitrireducens sp. nov., a soil bacterium performing nitrate reduction under low-temperature and microaerobic conditions

A facultative anaerobic spore-forming bacterium, designated OS1-33 T was isolated from apple orchard soil collected at Iksan-si, Republic of Korea. The phylogenetic position of the strain OS1-33 T was investigated by 16S rRNA gene sequence similarity analysis showing that it tightly clustered with species of the genus Neobacillus . The highest sequence similarity was observed to Neobacillus drentensis (99.93%). The genome of OS1-33 T showed an Average Nucleotide Identity (ANI) of less than 95% with all the other known type strains of Neobacillus species including N. drentensis DSM 15600 T . In addition, the digital DNA–DNA hybridization (dDDH) value between strain OS1-33 T and N. drentensis was 52.4% (95% confidence interval, 49.8%−55.1%), which is clearly below the 70% threshold for species delineation. The DNA G+C content of OS1-33 T was determined to be 38.92 mol%. Strain OS1-33 T exhibited nitrate reduction activity despite the presence of oxygen and at low temperature, suggesting that it may serve as a valuable microbial resource for nitrate removal in bioreactors operated under low-temperature conditions. Furthermore, distinct morphological, physiological, biochemical, and genomic characteristics differentiated strain OS1-33 T from its closest relatives. Based on overall results of the comparative analyses, strain OS1-33 T is proposed to represent a novel species within the genus Neobacillus , for which the name Neobacillus nitrireducens sp. nov. is proposed. The type strain is OS1-33 T (=KCCM 43525 T = JCM 38007 T ).