Proposal of three novel species of the family Xanthobacteraceae: Xanthobacter pollutisoli sp. nov., Xanthobacter luteus sp. nov. and Aquabacter albus sp. nov., isolated from oil-contaminated soils.
Three Gram-stain-negative bacterial strains, KR7-65T, KR7-225T and CN5-332T isolated from oil-contaminated soil in Korea and China were identified. Phylogenetic analysis based on 16S rRNA gene sequences placed the strains within the family Xanthobacteraceae, with KR7-65T and KR7-225T affiliated with the genus Xanthobacter and CN5-332T with the genus Aquabacter. Sequence similarities to type strains of validly published species were below 98.5%. Core genome phylogeny showed that the four strains formed distinct clusters occupying different positions in the phylogenetic tree and exhibited different closest relatives. Average nucleotide identity, average amino acid identity and digital DNA-DNA hybridization (dDDH) values between KR7-65T and KR7-225T and members of Xanthobacter were 78.7-87.0%, 74.8-87.8% and 22.7-32.3%, respectively, whereas those between CN5-332T and members of Aquabacter were 80.2-80.7%, 79.6-80.5% and 23.4-23.9%, supporting their assignment as novel species. The DNA G+C contents were 68.0, 69.9 and 66.5 mol% for KR7-65T, KR7-225T and CN5-332T, respectively. Strains KR7-65T and KR7-225T contained phosphatidylcholine, phosphatidylglycerol, phosphatidyl monomethyl ethanolamine, diphosphatidylglycerol (DPG) and an unidentified glycolipid as major polar lipids, whereas DPG was absent in strain CN5-332T. The primary fatty acids were summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c), cyclo C19 : 0ω8c and C16 : 0. On the basis of phylogenetic, genomic and phenotypic evidence, strains KR7-65T and KR7-225T represent two novel species of the genus Xanthobacter, for which the names Xanthobacter pollutisoli sp. nov. (type strain KR7-65T=KACC 23453T=NBRC 116939T) and Xanthobacter luteus sp. nov. (type strain KR7-225T=KACC 23282T=NBRC 116940T) are proposed. Strain CN5-332T represents a novel species of the genus Aquabacter, for which the name Aquabacter albus sp. nov. (type strain CN5-332T=KACC 23276T=CCTCC AB 2024343T) is proposed.