Salinimicrobium molybdatiresistens sp. nov., a novel molybdate-resistant and selenite-reducing bacterium isolated from river silt.

Strain TH3T was isolated from the river bottom silt collected in Hengshui, Hebei Province, China. The bacterium is a yellow-pigmented, rod-shaped, Gram-staining negative and aerobic organism. It was able to grow between 10 and 37 °C (optimum 30 °C), at pH values from 5.0 to 9.0 (optimum pH 7.0), and tolerated NaCl concentrations ranging from 0 to 13% (w/v, optimum 2%). The 16 S rRNA gene sequence of strain TH3T was found to be most closely related to Salinimicrobium sediminilitoris ASW11-47T (99.7%). Nevertheless, genome comparison revealed the relatedness indices below species delineation thresholds: digital DNA-DNA hybridization was 49.7%, and average nucleotide identity was 93.2%, and average amino acid identity was 94.2% compared to Salinimicrobium sediminilitoris ASW11-47T. Strain TH3T had a genome size of 3.7 Mb and a DNA G + C content of 41.0%. The major fatty acids observed for strain TH3T (≥ 5%) were iso-C14:0, iso-C15:0, anteiso-C15:0, iso-C16:0, iso-C16:0 3-OH, iso-C17:0 3-OH, and summed feature 3. The polar lipid composition included phosphatidylethanolamine, one unidentified phospholipid, two aminolipids, along with five unknown lipids. The sole respiratory quinone in strain TH3T was menaquinone-6. In addition, strain TH3T was highly resistant to molybdate (500 mM) and selenite (20 mM), and could completely reduce 1 mM selenite to red elemental SeNPs within 3 d. Strain TH3T contains several putative selenite-reducing genes, including sodA, serA, serC, cysH, deoC, tktA, and pdhC. Based on polyphasic characterization, strain TH3T was found to be a novel species in the genus Salinimicrobium, and the proposed name is Salinimicrobium molybdatiresistens sp. nov. The type strain is TH3T (= GDMCC 1.3399T = JCM 35713T).