Rhizobium cremeum sp. nov., isolated from sewage and capable of acquisition of heavy metal and aromatic compounds resistance genes

Two strains of Rhizobia isolated from sewage collected from the Chinese Baijiu distillery were characterized using a polyphasic approach. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strains W15^T and W16 were grouped as a separate clade closely related to Rhizobium daejeonense L61^T (98.6%). Multilocus sequence analysis (MLSA) with three housekeeping genes (recA, glnII and rpoA) also showed that strains W15^T and W16 belonged to the genus Rhizobium. Average nucleotide identity and digital DNA-DNA hybridization values between genome sequences of strain W15^T and the closely related species ranged from 77.0% to 87.8% and from 23.9% to 30.9%. The DNA G + C content of strain W15^T was 61.6 mol%. Strain W15^T contained Q-10 as the major ubiquinone and the dominant fatty acids were summed feature 8 (C _18:1ω7c and/or C _18:1ω6c; 73.1%) and C_18:0 (7.6%). The main polar lipids are phosphatidylcholine, phosphatidylmethylethanolamine, phosphatidylethanolamine and phosphatidylglycerol. On the basis of the evidences presented in this study, strains W15^T and W16 represents a novel species of the genus Rhizobium, for which the name Rhizobium cremeum sp. nov. is proposed. The type strain is W15^T (= CGMCC 1.18731^T = KACC 22344^T).