Sphingopyxis selenitireducens sp. nov. and Paeniglutamicibacter selenitireducens sp. nov., isolated from the rhizosphere of Cardamine hupingshanesis in Enshi, China

Two novel bacterial isolates were cultured from the rhizosphere of Cardamine hupingshanesis growing in Enshi, Hubei, China. Both strains are capable of reducing selenite to elemental selenium. Strain R3-92 T exhibited a high 16S rRNA gene sequence similarity (99.0%) to Sphingopyxis panaciterrae Gsoil 124 T , whilst strain R2-26 T showed a 16S rRNA gene sequence similarity of 99.5% to Paeniglutamicibacter kerguelensis KNG15 T . The phylogenetic analysis, based on whole-genome sequences and 92 core genes, positioned strain R3-92 T in the same cluster as Sphingopyxis witflariensis DSM 14551 T , and strain R2-26 T in the same cluster as P. kerguelensis DSM 15797 T . The genomes of strains R3-92 T and R2-26 T were 4.8 and 4.2 Mbp in size with DNA G+C contents of 63.6 mol% and 66.5 mol%, respectively. The average nucleotide identity (ANI) and digital DNA–DNA hybridization (dDDH) values for both strains, compared to their closest relatives, were below the species delineation threshold. Strain R3-92 T grew at 4–37 ℃, pH 5–9 and 0–4% (w/v) NaCl concentration, and its main fatty acids were summed feature 8 (C 18 : 1 ω 7 c and/or C 18 : 1 ω 6 c , 35.1%) and summed feature 3 (iso-C 15 : 0 2-OH and/or C 16 : 1 ω 7 c , 28.4%). Strain R2-26 T grew at 4–37 ℃, pH 6–9 and 0–8% (w/v) NaCl concentration, and its main fatty acids were anteiso-C 15 : 0 (62.2%) and anteiso-C 17 : 0 (14.1%). The combination of ANI results, dDDH results and phenotypic characteristics of strains R3-92 T and R2-26 T distinguishes them from their closely related strains. Based on the polyphasic analyses, strains R3-92 T and R2-26 T represent novel species of the genera Sphingopyxis and Paeniglutamicibacter , respectively, for which the names Sphingopyxis selenitireducens sp. nov. (type strain R3-92 T =GDMCC 1.4372 T =JCM 37246 T ) and Paeniglutamicibacter selenitireducens sp. nov. (type strain R2-26 T =GDMCC 1.4369 T =JCM 37299 T ) are proposed.