Sodium alginate-synthesizing regulatory gene algB in Pseudomonas putida XMS-1 decreases Cd uptake in Allium tuberosum in the Cd-polluted soil.

The Cd-tolerant and sodium alginate (SA)-synthesizing Pseudomonas putida XMS-1 was characterized for Cd immobilization in solution. Additionally, the XMS-1 mutant constructed by deleting SA-synthesizing regulatory gene algB (∆algB) were characterized for their roles in Cd uptake in Chinese chive in the Cd-contaminated soil. Between 12 and 48 h of incubation, the XMS-1∆algB mutant significantly reduced solution Cd concentrations by 81 % compared with the control but increased the Cd concentrations by 36 % compared with XMS-1. After 48 h of incubation, the XMS-1∆algB mutant significantly increased the Cd concentration by 36 % and decreased the expolysaccharide (EPS) and SA concentrations by 30 %-32 % and cell surface-adsorbed Cd content by 24 % in the Cd-containing medium, compared with XMS-1. The XMS-1∆algB mutant significantly increased the root and leaf Cd contents of Chinese chive by 15 %-50 % and exchangeable Cd content by 17 % and decreased the Fe-Mn oxide- and organic matter-bound Cd contents by 17 %-23 %, compared with XMS-1. Furthermore, the XMS-1∆algB mutant significantly decreased the EPS content by 33 %, copies of algD gene involved in EPS production by 7.7-fold, and the interactions between the amino, hydroxyl, and carbonyl groups and Cd in the Cd-contaminated soil, compared with XMS-1. These results suggested that algB promoted XMS-1-mediated Cd-stabilizing related gene abundance and interactions between soil and Cd and decreased Cd uptake in Chinese chive. These findings may provide an effective and eco-friendly way using SA-producing bacteria for safe production of vegetables in the Cd-polluted soil.