Bacterial bioreporter detects mercury in the presence of excess EDTA
Amy L. Dahl A D , John Sanseverino B and Jean-François Gaillard C
+ Author Affiliations
- Author Affiliations
A TechLaw, Inc., 101 Yesler Way, Suite 600, Seattle, WA 98104, USA.
B Center for Environmental Biotechnology, University of Tennessee, 676 Dabney Hall, Knoxville, TN 37996-1605, USA.
C Department of Civil and Environmental Engineering, Northwestern University, 2145 Sheridan Road, #A324, Evanston, IL 60208-3109, USA.
D Corresponding author. Email: adahl@techlawinc.com
Environmental Chemistry 8(6) 552-560 https://doi.org/10.1071/EN11043
Submitted: 6 April 2011 Accepted: 17 July 2011 Published: 13 September 2011
Environmental context. Understanding the uptake of mercury by bacteria is essential for predicting the amount of toxic methyl mercury formed in the environment. This study shows that the uptake of mercury by a whole-cell bacterial biosensor as a function of a strong ligand was greater than predicted by chemical speciation measurements or equilibrium calculations. These results call into question the use of chemical measurements and equilibrium modelling for predicting the toxicity of metals to living organisms in the environment and suggest that direct biological methods yield more accurate results.
Abstract. A whole-cell bacterial reporter was used to probe the bioavailability of mercury in the presence of a strong metal chelator, ethylenediaminetetraacetic acid (EDTA). Strain ARL1 was constructed by inserting a merR::luxCDABE fusion into the chromosome of Escherichia coli. The response of the bioreporter to HgII was monitored as a function of added EDTA. In parallel, square-wave voltammetry (SWV) measurements and thermodynamic calculations using MINEQL were performed to study the chemical speciation of mercury. The amount of electro-labile HgII measured by SWV was similar to the amount of non-complexed HgII predicted from equilibrium calculations. In contrast, the bioavailable fraction measured by the bioreporter was greater than the fraction predicted by either equilibrium calculation or electrochemical analysis. These results suggest that conventional chemical measurements and equilibrium calculations are not necessarily good proxies for predicting the bioavailable metal fraction. Additional factors such as kinetic effects or biological ligand competition must be considered.
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