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

Nowadays, there is limited research focusing on the biosorption of Pb 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 Pb, 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 Pb reached at 79.8%. The main mechanism of JC1 adsorb Pb is via intracellular accumulation, accounting for more than 90% of the total adsorption. At the physiological level, Pb 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 Pb outside of the cell wall, thus accomplishing extracellular adsorption of Pb 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 Pb by JC1. In addition, phosphate permease is a major member of the ABC transporter family involved in Pb, and czcA/cusA or Co/Mg efflux protein plays an important role in the efflux of Pb 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 Pb stress.