Luminescent bacteria-based sensing method for methylmercury specific determination

Abstract

A bacterial biosensor method for the selective determination of a bioavailable organomercurial compound, methylmercury, is presented. A recombinant luminescent whole-cell bacterial strain responding to total mercury content in samples was used. The bacterial cells were freeze-dried and used as robust, reagent-like compounds, without batch-to-batch variations. In this bacteria-based sensing method, luciferase is used as a reporter, which requires no substrate additions, therefore allowing homogenous, real-time monitoring of the reporter gene expression. A noninducible, constitutively light-producing control bacterial strain was included in parallel for determining the overall cytotoxicity of the samples. The specificity of the total mercury sensor Escherichia coli MC1061 (pmerRBlux) bacterial resistance system toward methylmercury is due to a coexpressed specific enzyme, organomercurial lyase. This enzyme mediates the cleavage of the carbon-mercury bond of methylmercury to yield mercury ions, which induce the reporter genes and produce a self-luminescent cell. The selective analysis of methylmercury with the total mercury strain is achieved by specifically chelating the inorganic mercury species from the sample using an optimized concentration of EDTA as a chelating agent. After the treatment with the chelating agent, a cross-reactivity of 0.2% with ionic mercury was observed at nonphysiological ionic mercury concentrations (100 nM). The assay was optimized to be performed in 3 h but results can already be read after 1 h incubation. Total mercury strain E. coli MC1061 (pmerRBlux) has been shown to be highly sensitive and capable of determining methylmercury at a subnanomolar level in optimized assay conditions with a very high dynamic range of two decades. The limit of detection of 75 ng/l (300 pM) allows measurement of methylmercury even from natural samples.

Bio‐Hybrid Cell‐Based Actuators for Microsystems

“…Finally, bio‐hybrid devices also have the potential to be used in environmental monitoring applications. Microorganisms are already being applied as sensors to detect agents such as salt, glucose, and heavy metal pollutants . Swarms of bio‐hybrid microswimmers could be deployed into a microenvironment, steered using external and cell‐based control methods, and be engaged to detect specific chemicals in a targeted region of interest.…”

Engineered cells as biosensing systems in biomedical analysis

“…Rantala et al [13] took a different approach to the detection of MeHg, one that focused on using an already engineered sensor [52], but creating a highly selective, more robust, reproducible, portable assay with detection limits down to 0.3 nmol L −1 levels. The whole-cell sensing system was constructed by transforming, in E. coli MC1061, a plasmid that fused the mercury inducible promoter and its regulatory gene, merR, from the pDU1358 mer-operon with reporter gene luxCDABE.…”

“…The reporter proteins encoded by such genes have also been used as signal-transduction elements in bacterial sensors. These proteins include β-galactosidase [11,12], bacterial luciferase [13], firefly luciferase [14], and the green fluorescent protein and its variants. Table 1 lists reporters that are commonly used in whole-cell sensing systems, with their catalyzed reactions and methods of detection.…”

Biosensor Design for Detection of Mercury in Contaminated Soil Using Rhamnolipid Biosurfactant and Luminescent Bacteria

“…e bioluminescent bacterium is a recombinant pmerRBPmerlux plasmid was transformed into the Escherichia coli strain MC 106 1 introduced by Rantala et al At the concentration of the cells was between 1 × 10 9 and 2 × 10 9 cells/tube, the high response of the E. coli cells was obtained [36]. Escherichia coli MC106 cells were grown at 37°C in a shaking incubator (Model: GFL 3032, Germany) at 200 rpm.…”