Assessing bioavailability and genotoxicity of heavy metals and metallic nanoparticles simultaneously using dual-sensing Escherichia coli whole-cell bioreporters

Abstract

Genetically engineered bacterial strains called whole-cell bioreporters (WCBs) generated by fusing the promoter region of stress-responsive genes and reporter genes have been widely used as biosensors to detect toxic materials in the environment. In this study, we report a dual-sensing WCB harboring recAp::egfp and zntAp::mcherry to measure the genotoxicity and bioavailability of heavy metals and metallic nanoparticles (NPs) simultaneously. Since the dual-sensing WCB harbored recAp::egfp and zntAp::mcherry, the genotoxicity and bioavailability of heavy metals and metallic NPs that activate ZntR would be assessed by measuring the fluorescence signal of enhanced green fluorescent protein (eGFP) and mCherry, respectively. Among the tested heavy metal(loid)s, only Cr induced both eGFP and mCherry expression, and some of them only induced mCherry, thereby suggesting that Cr is genotoxic. In case of the tested metallic NPs, Ti 2 O NPs, ZnO NPs, and Au NPs showed weak inhibitory effects on growth, but the eGFP was not induced. It was inferred that the tested NPs were not genotoxic and the inhibitory effects would not be related to direct DNA damage pathways. In addition, it was observed that ZnO NPs induced mCherry expression, indicating that the Zn ion was dissolved from the NPs. Although the dual-sensing WCB described here was limited to ZnO NPs, WCBs would be an alternative tool to investigate the dissolution of metallic NPs when the corresponding metal ion sensing systems were available.

Transcription Factor-Based Biosensors for Detecting Pathogens

“…Bacterial cell-based biosensors, also called whole-cell bioreporters, have been developed intensively during the last few decades and are regarded as an alternative tool for monitoring hazardous materials in our life [ 25 , 61 , 62 ]. With recent advances in biological technology, the applications of engineered whole-cell biosensors have expanded to environmental and medical fields for monitoring and detecting toxicants [ 63 , 64 ].…”

Inorganic Cadmium Detection Using a Fluorescent Whole-Cell Bacterial Bioreporter

“…However, depending on the toxicity levels and protein binding affinities of these metals, they are sensed at different concentrations. Bacterial bioreporters constructed using the promoter of the zntA gene as the sensing element are most sensitive to cadmium which induces the promoter at much lower concentrations than lead, zinc and mercury (Tauriainen et al 1998;Biran et al 2000;Ivask, Virta, and Kahru 2002;Kim and Yoon 2016).…”