title: Expression of arsenic regulatory protein in Escherichia coli for selective accumulation of methylated arsenic species.
abstract: ArsR is a metalloregulatory protein with high selectivity and affinity toward arsenic. We hereby report the expression of ArsR in Escherichia coli by cell engineering, which significantly enhances the adsorption/accumulation capacity of methylated arsenic species. The ArsR-expressed E. coli cells (denoted as E. coli-ArsR) give rise to 5.6-fold and 3.4-fold improvements on the adsorption/accumulation capacity for monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA), with respect to native E. coli cells. The uptake of MMA and DMA by the E. coli-ArsR is a fast process fitting Langmuir adsorption model. It is interesting to note that the accumulation of methylated arsenic is virtually not affected by the presence of competing heavy-metal species, at least 10 times of Cd(II) and Pb(II) are tolerated for the adsorption of 1 mg L(-1) methylated arsenic. In addition, an ionic strength of up to 2 g L(-1) Na+ poses no obvious effect on the sorption of 1 mg L(-1) MMA and DMA. Furthermore, the accumulation of MMA and DMA is less sensitive to the variation of pH value, with respect to the blank control cells. Consequently, 82.4% of MMA and 96.3% of DMA at a concentration of 50 μg L(-1) could be readily removed from aqueous medium by 12 g L(-1) of E. coli-ArsR . This illustrates a great potential for the E. coli-ArsR for selective remediation of methylated arsenic species in waters, even in the presence of a high concentration of salts.
authors.affiliation: Research Center for Analytical Sciences, College of Sciences, Box 332, Northeastern University, Shenyang 110819, People's Republic of China.
authors.forename: Ting
authors.initials: T
authors.lastname: Yang
authors.forename: Jia-Wei
authors.initials: JW
authors.lastname: Liu
authors.forename: Cuibo
authors.initials: C
authors.lastname: Gu
authors.forename: Ming-Li
authors.initials: ML
authors.lastname: Chen
authors.forename: Jian-Hua
authors.initials: JH
authors.lastname: Wang
mesh_terms: D000327:Adsorption; D001152:Arsenicals / Q000737:chemistry* / Q000378:metabolism; D001673:Biodegradation, Environmental; D018533:Biomass; D002101:Cacodylic Acid / Q000737:chemistry* / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*
chemical_list: C489527:ArsR protein, E coli; D001152:Arsenicals; D029968:Escherichia coli Proteins; D015534:Trans-Activators; D002101:Cacodylic Acid; C020300:monomethylarsonic acid