Absorption,Transport And Distribution Of Triclocarban And Cadmium By Bacteria

In environmental media,cadmium(Cd)pollution is widespread and serious,and the bioconcentration and persistence of triclocarban(TCC)are also receiving more and more attention.In this paper,the differences and regularity of absorption and transport of cadmium and triclocarba in Gram-negative bacteria Escherichia coli(E.coli)and Gram-positive bacteria Bacillus thuringiensis(B.thuringiensis)were studied by flow cytometry,LC/MS and other instruments.Cd and TCC inhibited the growth of E.coli and B.thuringiensis.This inhibition on B.thuringiensis was greater than that on E.coli.B.thuringiensis had lower adsorption for Cd than E.coli.The rate of adsorption of TCC by E.coli was faster than that of B.thuringiensis.The absorption and transport rates of TCC in E.coli and B.thuringiensis was higher than that of Cd.Cd was mainly distributed in the supernatant,reaching 96.5% in the E.coli culture system and 98.6% in the B.thuringiensis culture system.TCC was mainly distributed on the cell membrane and cell wall,reaching 52-81% in E.coli culture system and 49-76% in B.thuringiensis culture system.There were significant species differences in the adsorption of TCC and Cd on the bacterial surface,intracellular,membrane and wall.The stability constant of the bacteria to Cd was negative.Cd did not bind to the membrane.Therefore,Cd was effectively blocked by the cell membrane in the supernatant.The stability constant of E.coli,B.thuringiensis and liposome to TCC were 852.62,1954.34,845.34,respectively.The binding ability of TCC to cell wall was greater than that of the cell membrane.The peptidoglycan layer may be the target of TCC.Under the stress of pollutants,the cell membrane would be damaged.While in this work,Cd did not cause damage to the inner and outer membranes of E.coli and had no significant effect on bacterial membrane potential and permeability.Cd had no significant effect on the cell membrane of B.thuringiensis,but it increased the bacterial membrane potential and decreased membrane permeability.Under TCC stress,the outer membrane damage of E.coli decreased with time,the cell membrane showed no significant effect,and the membrane potential and permeability recovered with time.Under TCC stress,B.thuringiensis cell membrane damage increased with time,membrane potential decreased and membrane permeability increased.