Proteomics study on immobilization of Pb(II) by Penicillium polonicum

Lead (Pb) is widely distributed in nature and has important industrial applications, while being highly toxic. In this study, the Pb(II) biosorption and immobilization behavior of Penicillium polonicum was investigated through surface morphology observation and multiple experimental analysis. In addition, the molecular mechanism of Pb(II) immobilization was further explored through proteomics. The analysis of the removal ability of P. polonicum to Pb(II) has found that P. polonicum could remove Pb(II) up to 95% (initial 4 mM Pb(II)) in 12 d. Scanning Electron Microscope (SEM) revealed a large amount of Pb(II) adsorbed on the cell wall. Raman and Energy Disperse Spectroscopy (EDS) revealed the formation of large amounts of PbC2O4 minerals extracellularly. Field Emission High-resolution Transmission Electron Microscopy (FE-TEM) found that [Pb5(PO4)3Cl] formed on the cell surface and inside the cells. The iTRAQ technique was used to analyze the characteristics of the changes of proteins during the action between Pb(II) and P. polonicum, which further revealed the mechanism of P. polonicum against Pb(II) and biomineralization. It was found that differential proteins in terms of redox, ion binding, metabolic process and ribosome synthesis were predominant in the GO analysis. Together with some of the characterization experiments above, the mechanisms mentioned above was well explained. The up-regulated expression of related proteins involved in respiratory metabolic pathways, antioxidant stress, and degradation of intracellular hazardous substances in the P. polonicum intracellularly such as succinate dehydrogenase, ATPase and cytochrome c oxidase, could explain the high tolerance of P. polonicum to Pb(II). The up regulation of OAH was responsible for extracellular PbC2O4 production. The up regulation of proteins such as TXN and GFA promoted Pb-glutathione (Pb-GSH) complex formation. This study explores the mechanism of Pb removal by fungi from the proteomic level, and provides new ideas and ways for Pb biogeochemical research.