Expression And Function Identification Of Mer Manipulation Subsystem In Shewallena Oneidensis

In recent years,heavy metal pollution in the environment has posed a severe threat to the ecological balance in China,especially mercury（Hg）pollution.Therefore,the remediation of mercury in the environment is of vital importance.At present,there are many technologies to remediate mercury in the environment,mainly including physical and chemical remediation techniques.However,both of these methods have many problems,such as high remediation costs and the potential to cause secondary pollution.Microbial remediation is an environmentally friendly approach that can adsorb and fix heavy metal mercury without causing pollution.Thus,using microbes to remove mercury in the environment is the most promising environmental remediation technology to date.In this study,S.oneidensis MR-1 was selected as the experimental strain,and it was genetically modified to remove mercury from the environment.The engineered bacteria were then applied to the remediation of mercury pollution,particularly in aquatic environments.The Mer operon,a gene sequence involved in mercury removal,was optimized using genetic engineering and introduced into S.oneidensis MR-1.Protein expression levels were then measured.Engineered strain MRPB was tested for tolerance to Hg²⁺in water,and unmodified MR-1 was used as a control.Results showed that MRPB could grow at concentrations up to 180 mg/L of Hg²⁺,while MR-1 could only survive at concentrations below 100 mg/L.MRPB also adapted better to changes in environmental p H.Mercury removal experiments revealed that MRPB could achieve removal rates of 67%and 75%for Hg²⁺concentrations of 50 mg/L and 10 mg/L,respectively.SEM and TEM analyses revealed Hg0 on the bacterial surface,confirming that MRPB has excellent tolerance and mercury removal capabilities.The strains were cultured in microbial fuel cells（MFCs）to compare the voltage,power density,and current density of MFCs inoculated with two different strains.MRPB-inoculated MFCs reached a voltage of 170 m V,while MR-1-inoculated MFCs only achieved 140 m V.Electrochemical analysis indicated that MRPB had a higher capacitance ratio and lower Rct compared to MR-1.A higher capacitance ratio and lower Rct can accelerate the charge transfer rate and promote electricity generation.MRPB could remove 80%of Hg²⁺（10 mg/L）in MFCs.Scanning electron microscopy observations revealed that after the addition of Hg²⁺,MRPB could adhere normally to the carbon cloth,indicating better adhesion ability than MR-1.The results demonstrate that MRPB can enhance the extracellular electron transfer capacity of MFCs,providing a new research direction for Hg²⁺ removal.