An engineered microorganism can simultaneously detoxify cadmium, chlorpyrifos, and -hexachlorocyclohexane

Many ecosystems are currently co-contaminated with heavy metals such as cadmium (Cd2+) and pesticides such as chlorpyrifos (CP) and -hexachlorocyclohexane (-HCH). A feasible approach to remediate the combined pollution of heavy metals and pesticides is the use of -HCH degrading bacteria endowed with CP hydrolysis and heavy metal biosorption capabilities. In this work, a recombinant microorganism capable of simultaneously detoxifying Cd2+, CP, and -HCH was constructed by display of synthetic phytochelatins (EC20) and methyl parathion hydrolase (MPH) fusion protein on the cell surface of the -HCH degrading Sphingobium japonicum UT26 using the truncated ice nucleation protein (INPNC) as an anchoring motif. The surface localization of INPNC-EC20-MPH was verified by cell fractionation, Western blot analysis, immunofluorescence microscopy, and proteinase accessibility experiment. Expression of EC20 on the cell surface not only improved Cd2+ binding but also alleviated the cellular toxicity of Cd2+. As expected, the rates of CP and -HCH degradation were reduced in the presence of Cd2+ for cells without EC20 expression. However, expression of EC20 (higher Cd2+ accumulation) significantly restored the levels of CP and -HCH degradation. These results demonstrated that surface display of EC20 enhanced not only Cd2+ accumulation but also protected the recombinant strain against the toxic effects of Cd2+ on CP and -HCH degradation.