Rhodobacter xinxiangensis sp. nov., isolated from pakchoi-cultivated soil contaminated with heavy metal and its potential to reduce Cd and Pb accumulation in pakchoi (Brassica campestris L.).

A Gram-stain-negative, aerobic, and motile strain, TJ48(T), was isolated from pakchoi-cultivated soil contaminated with Cd and Pb in Xinxiang (China). Cells of the strain were rod-shaped and colonies on LB agar were faint yellow. Strain TJ48(T) was positive for catalase and oxidase and the optimal condition for growth was 28 degrees C, with 1% (w/v) NaCl and at pH 7.0. Phylogenetic analysis based on the 16S rRNA gene sequences showed that strain TJ48(T) was closely related to the genus Rhodobacter and the closest relatives were Rhodobacter ovatus JA234(T) (97.4%, 16S rRNA gene sequence similarity) and Rhodobacter azotoformans KA25(T) (96.5%). The DNA G + C content of strain TJ48(T) was 64.7 mol%. Genome-to-genome distance calculations (GGDC) and ANIb values from genomic comparison between the genomes of strain TJ48(T) and the related reference species were less than 70% and 95%, respectively. The major cellular fatty acids were summed feature 8 (C18:1omega7c and/or C18:1omega6c) and C17:0. The only isoprenoid quinone detected was Ubiquinone-10 (Q-10). The polar lipid profile contains diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, one unidentified aminophospholipid, one unidentified phospholipids, and three unidentified lipids. Strain TJ48(T) significantly increased the dry weight of roots (26.2-66.3%) and shoots (16.7-37.8%) of pakchoi and reduced the Cd (50.2-60.1%) and Pb (55.6-60.9%) contents in pakchoi shoots and roots. On the basis of the physiological, genotypic and genomic characteristics, the strain TJ48(T) represent a novel species of the genus Rhodobacter, and the name Rhodobacter xinxiangensis sp. nov. is proposed (type strain TJ48(T) = CCTCC AB2019120(T) = KCTC 72510(T)).