A novel strictly anaerobic sulfate-reducing diazotrophic bacterium sp. nov., isolated from paddy soil.

A strictly anaerobic sulfate-reducing strain, designated SG127, was isolated from paddy soil. SG127 showed the highest 16S rRNA gene sequence similarity to the type strain of (98.2 %). A phylogenetic tree based on 16S rRNA gene sequences indicated that SG127 clustered with members of the genus . Growth of SG127 was observed at 20-37 °C (optimum, 30 °C), pH 5.5-9.0 (optimum, 7.0-8.0) and with 0-0.2 % (w/v) NaCl (optimally without NaCl). SG127 contained MK-7 as the only menaquinone and anteiso-C, anteiso-Cω9, C, iso-C iso-C, iso-C iso-CH, iso-CH and summed feature nine as the major fatty acids. The genomic DNA G+C content of SG127 was 64.6 %. The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between SG127 and the closely related were 78.5% and 23.2 %, respectively, which were lower than the cut-off values (ANI 95-96% and dDDH 70 %) for prokaryotic species delineation. SG127 had desulfoviridin, possessed nitrogen fixation genes () and actively fixed nitrogen according to the acetylene reduction assay. On the basis of these results, strain SG127 represents a novel species of the genus , for which the name sp. nov. is proposed. The type strain is SG127 (= GDMCC 1.3137 = JCM 35589).