sp. nov., a novel bacterium from uranium mill tailings repository sites with selenium bioremediation capabilities.

A Gram-stain-negative bacterial strain designated Be4, belonging to the genus , was isolated from mining porewaters sampled in uranium mill tailings repository sites, located in Bellezane, near Bessines-sur-Gartempe (Limousin, France). Cells were facultative anaerobic, rod-shaped, non-endospore-forming and motile with flagella. The mean cell size was 1.25-1.31 μm long and 0.70-0.73 μm wide. Colonies were light yellow, opaque, circular, convex with smooth margins, and 1-2 mm in diameter. Growth occurs at 4-37 °C and between pH 5.5-9.0. It differed from its phylogenetically related strains by phenotypic and physiological characteristics such as growth at 4 °C, presence of acid phosphatase, naphthol-AS-BI-phosphohydrolase and β-glucosidase enzymatic activities, and fermentation of l-xylose and esculin. The major fatty acids were C, C ω7c/C ω6c, C cyclo and C ω7c. Phylogenetic analysis based on 16S rRNA and 938 core genes, confirmed its placement within the genus as a novel species. Strain Be4 showed highest 16S rRNA sequence similarity to (98.2 %), (97.9 %), (97.8 %) and (97.7 %). The genome of strain Be4 is 5,041,667 bp size with a DNA G + C content of 65.15 %. By automatic annotation numerous sequences involved in the interaction with metals/metalloids including some genes related to Se uptake and selenite resistance were detected in its genome. The average nucleotide identity (ANI) values calculated from whole genome sequences between strain Be4 and the most closely related strains and were below the threshold value of 95 %. Thus, the data from the phylogenetic, physiological, biochemical, and genomic analyses clearly indicates that strain Be4 represents a novel species with the suggested name sp. nov. The type strain is Be4 (=DSM116209 = CECT30865). This novel species, due to its unique isolation source, genomic analysis, and preliminary laboratory tests where it was able to reduce toxic Se(IV) to less harmful Se(0) in the form of nanoparticles, holds great potential for further investigation in bioremediation, particularly concerning Se.