Bacillus cereus LSP29 isolated from soil of the mining area can tolerate lead stress through antioxidation, adsorption, mineralization and molecular regulation

In this study, a high lead (Pb)-tolerant Bacillus cereus LSP29 was isolated from soil of the Hexi Corridor mining area in China, and the Pb tolerance mechanisms of the strain were revealed. The strain could tolerate up to 1200 mg/L Pb(II) in the liquid medium, with average maximum removal efficiencies of 86.93 % and 82.17 % at 40 h for 500 and 1000 mg/L Pb(II), respectively. Under Pb stress, the strain exhibited increased reactive oxygen species, malondialdehyde, and electrical conductivity, alongside enhanced synthesis of carotenoids, glutathione, and antioxidant enzyme activities. The adsorption process of LSP29 for Pb(II) followed the pseudo-second-order kinetic model and the Freundlich isothermal model. Both the strain cell and its extracellular polymeric substance participated in the Pb adsorption process through superficial -OH, -CH₂, CO, and C-O-P groups. Additionally, LSP29 facilitated Pb(II) mineralization into PbS crystals. Transcriptomic analysis identified 920 differentially expressed genes, highlighting upregulation in iron import, metal ion transport, oxidative phosphorylation, and sulfur relay systems, and downregulation in flagellum-dependent motility and small molecule catabolism. This study reveals a synergistic tolerance mechanism in strain LSP29 that integrates antioxidant defense, extracellular adsorption, biomineralization, and molecular regulation. These findings provide a theoretical foundation and suggest a potential microbial resource for the bioremediation of Pb-contaminated environments.