Achromobacter seleniivolatilans sp. nov. and Buttiauxella selenatireducens sp. nov., isolated from the rhizosphere of selenium hyperaccumulator Cardamine hupingshanesis

Two Gram-stain-negative bacterial strains, R39 and R73 , were isolated from the rhizosphere soil of the selenium hyperaccumulator in China. Strain R39 transformed selenite into elemental and volatile selenium, whereas strain R73 transformed both selenate and selenite into elemental selenium. Phylogenetic and phylogenomic analyses indicated that strain R39 belonged to the genus , while strain R73 belonged to the genus . Strain R39 (genome size, 6.68 Mb; G+C content, 61.6 mol%) showed the closest relationship to LMG 26219 and LMG 3441 , with average nucleotide identity (ANI) values of 83.6 and 83.4 %, respectively. Strain R73 (genome size, 5.22 Mb; G+C content, 50.3 mol%) was most closely related to ATCC 51602 with an ANI value of 86.4 %. Furthermore, strain A111 from the GenBank database was found to cluster with strain R73 within the genus through phylogenomic analyses. The ANI and digital DNA-DNA hybridization values between strains R73 and A111 were 97.5 and 80.0% respectively, indicating that they belong to the same species. Phenotypic characteristics also differentiated strain R39 and strain R73 from their closely related species. Based on the polyphasic analyses, strain R39 and strain R73 represent novel species of the genera and , respectively, for which the names sp. nov. (type strain R39 =GDMCC 1.3843 =JCM 36009 ) and sp. nov. (type strain R73 =GDMCC 1.3636 =JCM 35850 ) are proposed.