The effect of pvdA in the cadmium absorption by Pseudomonas umsongensis CR14 through metabolic analysis

In this study, the effects of the Cd-resistant and pyoverdine-producing strain Pseudomonas umsongensis CR14 on Cd stabilization and the mechanisms were investigated. Compared with the control, CR14 markedly reduced the Cd concentration in a Cd-containing solution. The genes pvdA, 4498, 4499, and pchF, which are associated with pyoverdine production, were identified in CR14. The mutants of genes concerning the production of pyoverdine were constructed. Among these mutants, the CR14ΔpvdA mutant showed a greater impact on Cd stabilization. The mutant CR14ΔpvdA brought a lower Cd concentration in the solution, with higher levels of cell surface-adsorbed and intracellular accumulated Cd, content of lipopolysaccharide (LPS), expression of the LPS producing genes lptD and lpxL, and cell surface particles. Additionally, CR14ΔpvdA demonstrated increased interactions between the hydroxyl, carboxyl, amino, or ether groups and Cd. These results suggest that the CR14ΔpvdA mutant immobilized Cd by increasing LPS production and cell surface particle numbers, upregulating the expression of LPS-producing genes, and increasing cell surface adsorption and intracellular accumulation in Cd-polluted solutions.