Comparative transcriptomics revealed the mechanism of Stenotrophomonas rhizophila JC1 response and biosorption to Pb²

Nowadays, there is limited research focusing on the biosorption of Pb²⁺ through microbial process, particularly at the level of gene expression. To overcome this knowledge gap, we studied the adsorption capacity of Stenotrophomonas rhizophila JC1 to Pb²⁺, and investigated the physiological mechanism by means of SEM, EDS, FTIR, membrane permeability detection, and investigated the molecular mechanism through comparative transcriptomics. The results showed that after 16 h of cultivation, the biosorption capacity of JC1 for 100 mg/L of Pb²⁺ reached at 79.8%. The main mechanism of JC1 adsorb Pb²⁺ is via intracellular accumulation, accounting for more than 90% of the total adsorption. At the physiological level, Pb²⁺ can precipitate with anion functional groups (e.g., -OH, -NH) on the bacterial cell wall or undergo replacement reaction with cell component elements (e.g., Si, Ca) to adsorb Pb²⁺ outside of the cell wall, thus accomplishing extracellular adsorption of Pb²⁺ by strains. Furthermore, the cell membrane acts as a "switch" that inhibits the entry of metal ions into the cell from the plasma membrane. At the molecular level, the gene pbt specificity is responsible for the adsorption of Pb²⁺ by JC1. In addition, phosphate permease is a major member of the ABC transporter family involved in Pb²⁺, and czcA/cusA or Co²⁺/Mg²⁺ efflux protein plays an important role in the efflux of Pb²⁺ in JC1. Further, cellular macromolecule biosynthesis, inorganic cation transmembrane transport, citrate cycle (TCA) and carbon metabolism pathways all play crucial roles in the response of strain JC1 to Pb²⁺ stress.