Polyphasic taxonomy of glacier-derived Variovorax strains reveals 13 novel species
Zi-Yun Chen1,2, Yu-Hua Xin1,3, Qing Liu1,3,4
1State Key Laboratory of Microbial Diversity and Innovative Utilization, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, PR China.
Abstract:
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 C16 : 0, summed feature 3 (C16:1 ω7c and/or C16:1 ω6c) and summed feature 8 (C18:1 ω7c and/or C18:1 ω6c). 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 1.10104T=NBRC 116946T), Variovorax frigidus sp. nov. (LT1R16ᵀ=CGMCC 1.11618T=NBRC 116947T), Variovorax trehalosi sp. nov. (LT1R20ᵀ=CGMCC 1.11621T=NBRC 116948T), Variovorax restrictus sp. nov. (LT1P1ᵀ=CGMCC 1.11725T=NBRC 116949T), Variovorax cryoconiti sp. nov. (LT2P21T=CGMCC 1.11737T=NBRC 116950T), Variovorax pasteuri sp. nov. (RB3P1T=CGMCC 1.11853T=NBRC 116951T), Variovorax nivicola sp. nov. (ZT5P49T=CGMCC 1.23581T=NBRC 116952T), Variovorax multivorans sp. nov. (ZT5R36T=CGMCC 1.23587T=NBRC 116953T), Variovorax nitratireducens sp. nov. (RT4R15T=CGMCC 1.24376T=NBRC 116954T), Variovorax monticola sp. nov. (GB4P3T=CGMCC 1.24632T=NBRC 116955T), Variovorax raffinosi sp. nov. (GB1P17T=CGMCC 1.24747T=NBRC 116956T), Variovorax glacialis sp. nov. (GT1P44T=CGMCC 1.24874T=NBRC 116957T) and Variovorax sucrosi sp. nov. (ZT4R33T=CGMCC 1.25067T=NBRC 116958T).
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