sp. nov.: A Novel Selenium-Resistant Bacterium Isolated from the Rhizosphere of in a Selenium-Rich Region of Enshi, Hubei Province.

ES5-4, a Gram-positive, motile, aerobic, and rod-shaped strain, was isolated from the rhizosphere of growing in the selenium-rich ore area of Enshi, Hubei Province, China. This strain can grow at pH levels of 5.0-10.0 and temperatures of 4-42 °C, with optimal growth at pH 7.0 and 28 °C. It was found to resist NaCl up to 5% (/), with an optimal growth condition of 0.5-1.0%. The strain exhibited tolerance to selenite (Se) concentrations up to 5000 mg/L. The major fatty acids of the ES5-4 strain were anteiso-C (46.5%) and C (21.7%), its predominant respiratory quinone was MK-7, and its polar lipids included diphosphatidylglycerol (DPG), phosphatidylethanolamine (PE), phosphatidylglycerol (PG), and an unidentified phospholipid (PL). The presence of the 16S rRNA gene sequence implies that ES5-4 belongs to a member of the genus , with the highest sequence similarity of 98.4% to NBRC 13638. The bac120 tree also confirmed that the strain is within the genus . The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between ES5-4 and closely related members of the genus were all below the cutoff levels of 95-96% and 70%, respectively. Based on a polyphasic approach, including phenotypic, chemotaxonomic, and phylogenetic analyses, the ES5-4 strain is proposed as a novel species of the genus , for which the name sp. nov. is proposed. This type strain is designated as ES5-4 (=GDMCC 1.3540 = KCTC 43478).