Sulfate-reducing bacteria block cadmium and lead uptake in rice by regulating sulfur metabolism.

Abstract

Aim: This study was dedicated to investigating the role of sulfur metabolic processes in sulfate-reducing bacteria in plant resistance to heavy metal contamination.

Methods and results: We constructed sulfate-reducing bacterial communities based on the functional properties of sulfate-reducing strains, and then screened out the most effective sulfate-reducing bacterial community SYN1, that prevented Cd and Pb uptake in rice through hydroponic experiment. This community lowered Cd levels in the roots and upper roots by 36.60% and 39.88%, respectively, and Pb levels by 35.96% and 51.54%. We also compared two treatment groups, inoculated with SYN1 and exogenously added GSH, and found that both enhanced the antioxidant response of the plants, increased the lignin and GSH contents and the expression of genes related to the phenylpropane biosynthesis pathway (OsCAD, Os4CL, OsCOMT, OsPOD, OsC3H, and OsPAL), and decreased the expression of heavy metal transporter genes (OsHMA2, OsIRT1) expression. There were no significant differences between the two treatments.

Conclusions: Sulfate-reducing bacteria produce GSH through the sulfur assimilation pathway, and GSH can directly chelate heavy metals or enhance plant antioxidant enzyme activities and regulate processes such as uptake and translocation of heavy metals, thus enhancing plant resistance to heavy metal toxicity.