Chitosan hydrogel microspheres loaded with Bacillus subtilis promote plant growth and reduce chromium uptake.

Cr contamination can lead to reduced crop yields and threaten food security. Eliminating soil Cr contamination or improving crop resistance to Cr is challenging in terms of costly, environment and biodiversity risk. Here, we used chitosan hydrogel microspheres loaded with Bacillus subtilis to cope with plant stress caused by Cr contamination. The addition of chitosan hydrogel microspheres loaded with Bacillus subtilis increased shoot biomass by 88 % and decreased the plant Cr concentration by 17 %. The bacterial chitosan hydrogel microsphere treatment enhanced the decomposition of organic matter and facilitated the uptake of nutrients by the plants. It also significantly increased the abundance of anti-heavy metal stress functional bacteria (Proteobacteria, Actinobacteria, and Chloroflexi), strongly promoting interactions and correlations between microbes. This technology of bacterial-chitosan hydrogel microspheres presents promising opportunities for sustainable strategies for addressing heavy metal pollution and enhancing agricultural productivity.