Polyphasic taxonomy of glacier-derived Variovorax strains reveals 13 novel species

Seventeen bacterial strains were isolated from cryoconite and glacial ice samples collected from five glaciers in China. Phylogenetic analyses based on 16S rRNA gene sequences placed these strains within the genus Variovorax . Pairwise average nucleotide identity (ANI) and digital DNA–DNA hybridization (dDDH) comparisons among the 17 strains supported their assignment to 13 separate genomic species. The highest ANI (≤94.2%) and dDDH (≤60.5%) values between them and their closest type strains were below the accepted species thresholds, indicating that they cannot be assigned to any known Variovorax species. Consistently, the phylogenomic tree resolved 13 well-supported, independent lineages corresponding to these genomic species. The major cellular fatty acids in the majority of strains were C 16 : 0 , summed feature 3 (C 16:1 ω 7 c and/or C 16:1 ω 6 c ) and summed feature 8 (C 18:1 ω7c and/or C 18:1 ω 6 c ). Based on combined phenotypic, genotypic and phylogenetic evidence, the 17 strains represent 13 novel species of the genus Variovorax , for which the following names are proposed: Variovorax glucosi sp. nov. (RHLX14ᵀ=CGMCC 1.10104 T =NBRC 116946 T ), Variovorax frigidus sp. nov. (LT1R16ᵀ=CGMCC 1.11618 T =NBRC 116947 T ), Variovorax trehalosi sp. nov. (LT1R20ᵀ=CGMCC 1.11621 T =NBRC 116948 T ), Variovorax restrictus sp. nov. (LT1P1ᵀ=CGMCC 1.11725 T =NBRC 116949 T ), Variovorax cryoconiti sp. nov. (LT2P21 T =CGMCC 1.11737 T =NBRC 116950 T ), Variovorax pasteuri sp. nov. (RB3P1 T =CGMCC 1.11853 T =NBRC 116951 T ), Variovorax nivicola sp. nov. (ZT5P49 T =CGMCC 1.23581 T =NBRC 116952 T ), Variovorax multivorans sp. nov. (ZT5R36 T =CGMCC 1.23587 T =NBRC 116953 T ), Variovorax nitratireducens sp. nov. (RT4R15 T =CGMCC 1.24376 T =NBRC 116954 T ), Variovorax monticola sp. nov. (GB4P3 T =CGMCC 1.24632 T =NBRC 116955 T ), Variovorax raffinosi sp. nov. (GB1P17 T =CGMCC 1.24747 T =NBRC 116956 T ), Variovorax glacialis sp. nov. (GT1P44 T =CGMCC 1.24874 T =NBRC 116957 T ) and Variovorax sucrosi sp. nov. (ZT4R33 T =CGMCC 1.25067 T =NBRC 116958 T ).