Highly Sensitive Luminescent Bioassay Using Recombinant Escherichia coli Biosensor for Rapid Detection of Low Cr(VI) Concentration in Environmental Water

Abstract

In this study, we constructed a recombinant Escherichia coli strain with different promoters inserted between the chromate-sensing regulator chrB and the reporter gene luxAB to sense low hexavalent chromium (Cr(VI)) concentrations (<0.05 mg/L); subsequently, its biosensor characteristics (sensitivity, selectivity, and specificity) for measuring Cr(VI) in various water bodies were evaluated. The luminescence intensity of each biosensor depended on pH, temperature, detection time, coexisting carbon source, coexisting ion, Cr(VI) oxyanion form, Cr(VI) concentration, cell type, and type of medium. Recombinant lux-expressing E. coli with the T7 promoter (T7-lux-E. coli, limit of detection (LOD) = 0.0005 mg/L) had the highest luminescence intensity or was the most sensitive for Cr(VI) detection, followed by E. coli with the T3 promoter (T3-lux-E. coli, LOD = 0.001 mg/L) and that with the SP6 promoter (SP6-lux-E. coli, LOD = 0.005 mg/L). All biosensors could be used to determine whether the Cr(VI) standard was met in terms of water quality, even when using thawing frozen cells as biosensors after 90-day cryogenic storage. The SP6-lux-E. coli biosensor had the shortest detection time (0.5 h) and the highest adaptability to environmental interference. The T7-lux-E. coli biosensor—with the optimal LOD, a wide measurement range (0.0005–0.5 mg/L), and low deviation (−5.0–7.9%) in detecting Cr(VI) from industrial effluents, domestic effluents, and surface water—is an efficient Cr(VI) biosensor. This unprecedented study is to evaluate recombinant lux E. coli with dissimilar promoters for their possible practice in Cr(VI) measurement in water bodies, and the biosensor performance is clearly superior to that of past systems in terms of detection time, LOD, and detection deviation for real water samples.

Ferrous Industrial Wastes—Valuable Resources for Water and Wastewater Decontamination

“…Regarding wastewater contamination, Cr (VI) is one of the monitored pollutants due to its high toxicity, both to humans and animals, but also to its mobility in the soil, so it can also appear in groundwater [ 140 , 141 ]. The less toxic form, Cr(III), precipitates more easily in the form of Cr(OH) 3 , but also in combinations with Fe(III) in the form of oxy(hydroxides), at alkaline or slightly acidic pH [ 142 , 143 , 144 , 145 ].…”

Transcriptomics extract the key chromium resistance genes of Cellulomonas

“…ChrA can actively recognize CrO 4 2− ions and expel CrO 4 2− ions out of the cell through proton dynamics with energy consumption [10]. ChrB protein can positively regulate the function of ChrA, promoting the e ux of Cr(VI) from the cell and enhancing the active extrusion of Cr(VI) by the cell [11]. In addition, some ABC transmembrane transport proteins can also facilitate the e ux of certain intracellular heavy metals.…”

Validation of a Standard Luminescence Method for the Fast Determination of the Antimicrobial Activity of Nanoparticles in Escherichia coli

“…Such an example is the use of luminescent E. coli for the detection of β-lactams [33] or as light-on/light-off sensors for bioavailable heavy metals, such as copper and mercury [34]. Interestingly, little effort has been made in the establishment of straightforward, standardized approaches fully devoted to the determination of the antimicrobial activity of nanoparticles and nanoformulations, where in-lab pre-modified strains or special genetic constructs are needed [35,36]. An example of such is the one-time reported use of luminescent E. coli strains on the investigation of copper nanoparticles' possible antibacterial mechanisms [37].…”