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