Transportation And Transformation Mechanism Of Cu(?) At The Cell Interface Of Klebsiella Spp.

With the rapid development of modern industry and mining industry,a large number of wastewater and waste residue containing heavy metals are also discharged in the production process.The heavy metals contained in the waste water and residue will migrate into the surface runoff,soil and groundwater,and eventually enter the organism from the food chain to enrich,and combine with the organic matter in the organism to transform into toxic substances,thus causing serious damage to the biological tissues for a long time.In order to deal with the more and more serious heavy metal pollution in recent years,economic,environmental protection and efficient microbial remediation technology has become a research hotspot;among them,a variety of bacteria are widely used in the treatment of heavy metal pollution.In order to further develop and improve this technology,it is necessary to master the mechanism of heavy metal adsorption and removal by bacteria.However,the mechanism of heavy metal removal by bacteria at the cell level is not clear.Only by mastering the mechanism of heavy metal migration and transformation in and out of bacterial cells can we make a fundamental explanation of the principle of microbial activated sludge method,which is widely used in heavy metal pollution treatment,so as to provide theoretical support for improving microbial remediation technology and process.In this paper,Klebsiella acidogenes was used as the experimental bacteria to study the migration and transformation mechanism of Cu²⁺in and out of bacterial cells.Among them,the minimum inhibitory concentration?MIC?and the maximum tolerable concentration?MTC?of Cu²⁺were measured by OD₆₀₀00 growth curve method;the cell components were separated by differential centrifugation and density gradient centrifugation,and the distribution of Cu²⁺in cell components after adsorption test was measured;the analysis was carried out by XPS The migration and distribution of various elements in different initial Cu²⁺concentration were studied.The valence changes of Cu²⁺on cell wall and cell membrane were analyzed by AES peak fitting.The dominant group of Cu²⁺adsorption was analyzed by FT-IR.The K⁺channel blocker?Green Mamba venom?and Ca²⁺channel blocker?lanthanum chloride?was used to analyze the ion exchange mechanism of Cu²⁺and Cu²⁺at cell wall and cell membrane interface.Finally,the mathematical characteristics of Cu²⁺migration in cell were studied by the method of adsorption kinetics subsection fitting.The results show that:The optimal pH value was 4.0;MIC=10mg/L,MTC=60mg/L;the removal rate of Cu²⁺by Klebsiella acidophilus was up to 68.2%,and the removal rate of Cu²⁺by a unit mass of bacteria was up to 102.45mg/g;when the initial concentration was less than 20mg/L,Cu²⁺did not migrate to the cell wall and cell membrane interface,and extracellular polymer played a major role in the removal of Cu²⁺;when the initial concentration was between 20 and 30mg/L,the adsorption process can be divided into three stages:the first stage is extracellular polymer adsorption stage;the second stage is extracellular polymer adsorption,cell wall and membrane interface adsorption,and cell transportation and transformation coexist;the third stage is that the adsorption of Cu²⁺by extracellular polymer reaches saturation,only cell wall and cell membrane adsorption,cell transportation and transformation coexist,but fine The adsorption rate of Cu²⁺on cell wall and cell membrane is higher than that of Cu²⁺from cell wall and membrane interface to intracellular migration;when the initial concentration is higher than 30 mg/L,the adsorption rate of Cu²⁺on extracellular polymer,cell wall and cell membrane reaches saturation,and the adsorption rate of Cu²⁺on cell wall and cell membrane is equal to the migration rate of Cu²⁺from cell wall and membrane interface to intracellular migration,and the intracellular Cu²⁺is accumulating continuously;Cu⁺will induce;The cell produces sulfhydryl thioprotein,which can be removed by binding with copper ions;Cu²⁺reacts with redox on the cell wall and is reduced to Cu⁺;Cu⁺and K⁺exchange with each other on the cell membrane,each exchange enters into one Cu⁺in the cell and discharges two K⁺out of the cell;Cu²⁺and Ca²⁺exchange with each other on the cell wall,each exchange enters into one Cu²⁺in the cell wall and discharges one Ca²⁺out of the cell;when the initial Cu²⁺concentration is less than 20mg/L,the extracellular polymer plays a leading role in the adsorption,and the whole adsorption process conforms to the quasi second-order kinetic model;when the initial Cu²⁺concentration is greater than 20mg/L,it conforms to the quasi second-order kinetic model in the fitting interval of 0-8 hours;it conforms to the quasi first-order kinetic model in the fitting interval of 0-16 hours.