Metal-tolerant Enterobacter sp. strain EG16 enhanced phytoremediation using Hibiscus cannabinus via siderophore-mediated plant growth promotion under metal contamination.

Aims: This study is aimed to investigate the efficiency of plant growth-promoting (PGP) strategies of Enterobacter sp. strain EG16 under metal stress and its potential application in phytoremediation. Methods: Production of siderophores and indole-3-acetic acid (IAA) by EG16 were assessed in a hydroponic system in which Hibiscus cannabinus was grown with different concentrations of Cd and Fe. A pot experiment was also carried out to evaluate the practical effect of EG16 on H. cannabinus growth and remediation efficiency. Results: Inoculation with EG16 significantly improved plant growth, probably as a result of increased plant uptake of Fe and immobilization of Cd, which resulted in decreased plant accumulation of Cd. Increased production of siderophores by EG16 in response to Cd exposure appeared to be the PGP strategy functioning in the EG16- H. cannabinus association. The bacterial Cd response system promoted plant and bacterial uptake of Fe, alleviated Cd-induced inhibition of bacterial IAA production, and potentially assisted in metal immobilization in the rhizosphere. Conclusions: The EG16- H. cannabinus association may be useful for phytostabilization, as it exhibits good plant growth, low plant accumulation of metals, and reduced metal bioavailability in soil. [ABSTRACT FROM AUTHOR]