Cedecea selenatireducens sp. nov. and Rahnella selenatireducens sp. nov., isolated from the seleniferous soil

Two Gram-stain-negative bacterial strains, designated S5-13 T and S5-11 T , were isolated from seleniferous soil in Enshi, PR China. Both strains demonstrated the ability to tolerate high concentrations of selenite and selenate and efficiently reduced these selenium oxyanions to elemental selenium. Phylogenetic and phylogenomic analyses revealed that strain S5-13 T belongs to the genus Cedecea , while S5-11 T is affiliated with the genus Rahnella . Strain S5-13 T (genome size, 4.77 Mb; G+C content, 55.1 mol%) exhibited the closest relationship to Cedecea neteri ATCC 33855 T with an average nucleotide identity (ANI) value of 91.4% and a digital DNA–DNA hybridization (dDDH) value of 46.2%. Additionally, phylogenomic analyses identified strain SSMD04 from the GenBank database as clustering within the genus Cedecea alongside strain S5-13 T . The ANI and dDDH values between strains S5-13 T and SSMD04 were 99.2% and 93.8 %, respectively, confirming their classification as the same species. Strain S5-11 T (genome size, 5.45 Mb; G+C content, 52.4 mol%) showed the closest phylogenetic affinity to Rahnella laticis SAP-17 T and Rahnella contaminans Lac-M11 T , with ANI values of 94.4% and 92.7 %, respectively. S5-13 T and S5-11 T contained C 16:0 and C 17:0 cyclo as the dominant fatty acids. Phenotypic characteristics further distinguished strains S5-13 T and S5-11 T from their closest relatives. Based on these results, strain S5-13 T and S5-11 T represent novel species within the genera Cedecea and Rahnella , for which the names Cedecea selenatireducens sp. nov. (type strain S5-13 T =GDMCC 1.4366 T =JCM 37117 T ) and Rahnella selenatireducens sp. nov. (type strain S5-11 T =GDMCC 1.4365 T =JCM 37116 T ) are proposed.