Bacterial bioreporter detects mercury in the presence of excess EDTA

2011 ◽  
Vol 8 (6) ◽  
pp. 552 ◽  
Author(s):  
Amy L. Dahl ◽  
John Sanseverino ◽  
Jean-François Gaillard
Keyword(s):  
Chemical Speciation ◽  
Ethylenediaminetetraacetic Acid ◽  
Electrochemical Analysis ◽  
Bacterial Biosensor ◽  
Whole Cell ◽  
Bioavailable Fraction ◽  
Chemical Measurements ◽  
Kinetic Effects ◽  
Living Organisms ◽  
Equilibrium Calculations

Environmental contextUnderstanding 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. AbstractA 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.

scholarly journals Versatile artificial mer operons in Escherichia coli towards whole cell biosensing and adsorption of mercury

PLoS ONE ◽  
2021 ◽  
Vol 16 (5) ◽  
pp. e0252190
Author(s):  
Nai-xing Zhang ◽  
Yan Guo ◽  
Hui Li ◽  
Xue-Qin Yang ◽  
Chao-xian Gao ◽  
...  
Keyword(s):  
Heavy Metal ◽  
Surface Display ◽  
Fluorescence Emission ◽  
Cell Surface Display ◽  
Heavy Metal Resistance ◽  
Metal Resistance ◽  
Whole Cell ◽  
Bioavailable Fraction ◽  
High Concentrations ◽  
Living Organisms

Mercury exists naturally and mainly as a man-made pollutant in the environment, where it exerts adverse effects on local ecosystems and living organisms. It is important to develop an appropriate synthetic biological device that recognizes, detects and removes the bioavailable fraction of environmental mercury. Both single-signal and double-signal output mercury biosensors were assembled using a natural mer operon as a template. Selectivity and sensitivity of whole-cell biosensors based on artificial mer operons were determined. Three whole-cell biosensors were highly stable at very high concentrations of mercuric chloride, and could detect bioavailable Hg(II) in the concentration range of 6.25–200 μM HgCl2. A novel Hg(II) bioadsorption coupled with biosensing artificial mer operon was assembled. This would allow Hg(II)-induced Hg(II) binding protein cell surface display and green fluorescence emission to be achieved simultaneously while retaining the linear relationship between fluorescent signal and Hg(II) exposure concentration. The present study provides an innovative way to simultaneously detect, quantify, and remove bioavailable heavy metal ions using an artificially reconstructed heavy metal resistance operon.

A Whole-Cell Bacterial Biosensor for Blood Markers Detection in Urine

2021 ◽  
Author(s):  
Natalia Barger ◽  
Ilan Oren ◽  
Ximing Li ◽  
Mouna Habib ◽  
Ramez Daniel
Keyword(s):  
Bacterial Biosensor ◽  
Whole Cell

scholarly journals Chemical Speciation of some Heavy Metals in Sand Filter Media [SFM] Waste Dumpsite in Yenagoa, Nigeria

2020 ◽  
Vol 24 (4) ◽  
pp. 549-556
Author(s):  
I.L. Ikoko ◽  
C.I. Osu ◽  
M. Horsfall
Keyword(s):  
Heavy Metals ◽  
Chemical Speciation ◽  
Total Concentration ◽  
Speciation Analysis ◽  
Filter Media ◽  
Sand Filter ◽  
Exchangeable Fraction ◽  
Sequential Extraction Method ◽  
Chemical Availability ◽  
Living Organisms

The chemical speciation of five heavy metals [HMs] in spent sand-filter-media [SFM] waste dumpsite was investigated with a view to ascertain their distribution and chemical availability of the heavy metals in the dumpsite. Samples were collected at the surface, 100cm depth of the dumpsite and 100m away from the dumpsite and analysed using FAAS for total concentration of Cr, Fe, Mn. Ni and Pb. Speciation analysis was carried out usingmodified Tessier’s sequential extraction method. The percentage concentrations showed that Pb occurred more at the exchangeable fraction with 90.6% at the top, 91.34% at 100cm depth. This signifies that Pb is biochemically available for in-take by living organisms. Fe had the highest concentration by mass 12mg/g but its occurrence of between 22- 28% is in the residual/inert fraction. Ni had 40% in the exchangeable and  carbonate fractions at the surface and at 100cm depth. Cr had highest exchangeable fraction of 46.29% and 45.59% at the surface and 100cm depth of the SFM. Mn had 37.30% and 42.26% at the surface and at 100cm depth of the SFM. Although Fe had highest concentration by mass, it is least biochemically available occurring more at the residual/inert fraction while the other four metals [Pb, Ni, Cr, Mn] are all biochemically available for intake by organisms and may enhance biochemical accumulation overtime and finally become harmful to living organisms around that dumpsite. Keywords: Speciation, Heavy metals, Sand Filter Media, Waste Dumpsite

scholarly journals A Whole-Cell Phenotypic Screening Platform for Identifying Methylerythritol Phosphate Pathway-Selective Inhibitors as Novel Antibacterial Agents

2012 ◽  
Vol 56 (9) ◽  
pp. 4906-4913 ◽  
Author(s):  
Charles A. Testa ◽  
L. Jeffrey Johnson
Keyword(s):  
High Throughput Screening ◽  
Mep Pathway ◽  
Phenotypic Screening ◽  
Mva Pathway ◽  
Whole Cell ◽  
Content Type ◽  
Methylerythritol Phosphate ◽  
Serovar Typhimurium ◽  
Living Organisms ◽  
Screening Platform

ABSTRACTIsoprenoid biosynthesis is essential for survival of all living organisms. More than 50,000 unique isoprenoids occur naturally, with each constructed from two simple five-carbon precursors: isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP). Two pathways for the biosynthesis of IPP and DMAPP are found in nature. Humans exclusively use the mevalonate (MVA) pathway, while most bacteria, including all Gram-negative and many Gram-positive species, use the unrelated methylerythritol phosphate (MEP) pathway. Here we report the development of a novel, whole-cell phenotypic screening platform to identify compounds that selectively inhibit the MEP pathway. Strains ofSalmonella entericaserovar Typhimurium were engineered to have separately inducible MEP (native) and MVA (nonnative) pathways. These strains, RMC26 and CT31-7d, were then used to differentiate MVA pathway- and MEP pathway-specific perturbation. Compounds that inhibit MEP pathway-dependent bacterial growth but leave MVA-dependent growth unaffected represent MEP pathway-selective antibacterials. This screening platform offers three significant results. First, the compound is antibacterial and is therefore cell permeant, enabling access to the intracellular target. Second, the compound inhibits one or more MEP pathway enzymes. Third, the MVA pathway is unaffected, suggesting selectivity for targeting the bacterial versus host pathway. The cell lines also display increased sensitivity to two reported MEP pathway-specific inhibitors, further biasing the platform toward inhibitors selective for the MEP pathway. We demonstrate development of a robust, high-throughput screening platform that combines phenotypic and target-based screening that can identify MEP pathway-selective antibacterials simply by monitoring optical density as the readout for cell growth/inhibition.

Redox Reactions in Lipid Membranes as a Model for Primordial Energy-Conserving Systems

1997 ◽  
Vol 161 ◽  
pp. 437-442
Author(s):  
Salvatore Di Bernardo ◽  
Romana Fato ◽  
Giorgio Lenaz
Keyword(s):  
Experimental Evidence ◽  
Lipid Membranes ◽  
Energy Supply ◽  
Redox Reactions ◽  
Living Systems ◽  
Asymmetric Distribution ◽  
Conservation Of Energy ◽  
Asymmetrical Distribution ◽  
Energy Conserving ◽  
Living Organisms

AbstractOne of the peculiar aspects of living systems is the production and conservation of energy. This aspect is provided by specialized organelles, such as the mitochondria and chloroplasts, in developed living organisms. In primordial systems lacking specialized enzymatic complexes the energy supply was probably bound to the generation and maintenance of an asymmetric distribution of charged molecules in compartmentalized systems. On the basis of experimental evidence, we suggest that lipophilic quinones were involved in the generation of this asymmetrical distribution of charges through vectorial redox reactions across lipid membranes.

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