A highly sensitive biosensor with a single-copy evolved sensing cassette for chlorpyrifos pesticide detection

Harnessing the power of biosensors for environmental monitoring of pesticides in water

The current strong reliance on synthetic chemicals, namely pesticides, is far from environmentally sustainable. These xenobiotics contribute significantly to global change and to the current biodiversity crisis, but have been overlooked when compared to other agents (e.g., climate change). Aquatic ecosystems are particularly vulnerable to pesticides, making monitoring programs essential to preserve ecosystem health, safeguard biodiversity, ensure water quality, and mitigate potential human health risks associated with contaminated water sources. Biosensors show great potential as time/cost-effective and disposable systems for the high-throughput detection (and quantification) of these pollutants. In this mini-review, we provide an overview of biosensors specifically developed for environmental water monitoring, covering different pesticide classes (and active ingredients), and types of biosensors (according to the bio-recognition element) and transducers, as well as the nature of sample matrices analyzed. We highlight the variety of biosensors that have been developed and successfully applied to detection of pesticides in aqueous samples, including enzymatic biosensors, immunosensors, aptasensors, and whole cell-based biosensors. While most biosensors have been designed to detect insecticides, expanding their compound target range could significantly streamline monitoring of environmental contaminants. Despite limitations related to stability, reproducibility, and interference from environmental factors, biosensors represent a promising and sustainable technology for pesticide monitoring in the aquatic environments, offering sensitivity and specificity, as well as portability and real-time results. We propose that biosensors would be most effective as an initial screening step in a tiered assessment, complementing conventional methods. KEY POINTS: • Pesticides harm aquatic ecosystems and biodiversity, requiring better monitoring • Biosensors offer cost-effective solutions to detect pesticides in water samples • Biosensors complement conventional methods as a sustainable tool for initial screens.

Visual signal transduction for environmental stewardship: A novel biosensing approach to identify and quantify chlorpyrifos-related residues in aquatic environments

The pervasive presence of organophosphate pesticides (OPs), such as chlorpyrifos (CPF), in aquatic ecosystems underscores the urgent need for sensitive and reliable detection methods to safeguard environmental and public health. This study addressed the critical need for a novel biosensor capable of detecting CPF and its toxic metabolite, 3,5,6-trichloro-2-pyridinol (TCP), with high sensitivity and selectivity, suitable for field applications in environmental monitoring. The study engineered a whole-cell biosensor based on E. coli strains that utilize the ChpR transcriptional regulator and the vioABCE gene cluster, providing a distinct visual and colorimetric response to CPF and TCP. The biosensor's performance was optimized and evaluated across various water matrices, including freshwater, seawater, and soil leachate. The biosensor demonstrated high sensitivity with a broad linear detection range, achieving limits of detection (LODs) at 0.8 μM for CPF and 7.813 nM for TCP. The linear regression concentration ranges were 1.6-12.5 μM for CPF and 15.6-125 nM for TCP, aligning with environmental standard limits and ensuring the biosensor's effectiveness in real-world scenarios. This innovative biosensing approach offers a robust, user-friendly tool for on-site environmental monitoring, significantly mitigating OPs contamination and advancing current detection technologies to meet environmental protection standards.

The potential of microorganisms as biomonitoring and bioremediation tools for mercury-contaminated soils

Mercury (Hg) pollution is a global issue due to the high toxicity and wide dispersion of Hg around the world. Whether due to anthropogenic activities or natural processes, Hg emissions are steadily increasing, with very high levels in some regions, directly threatening human and ecosystem health. However, bacteria and fungi have evolved and adapted in response to Hg-induced stress and have developed tolerance mechanisms, notably based on the mer operon system that is involved in Hg uptake and biovolatilization via Hg reduction reactions. Other processes, such as bioaccumulation or extracellular sequestration, are involved in Hg resistance, and the study of contaminated soils has allowed the isolation of a number of microorganisms capable of these mechanisms, with strong potential for the implementation of bioremediation approaches. In addition to playing an important role in determining the fate of Hg in the biogeochemical cycle, these microorganisms can indeed be applied to reduce Hg concentrations or at least stabilize Hg for the remediation of polluted soils. Moreover, thanks to the development of biotechnological tools, bioremediation based on Hg-tolerant microorganisms can be optimized. Finally, these microorganisms are relevant candidates for biomonitoring, for example, through the engineering of biosensors, because the detection of Hg is a major issue in preserving the health of living beings.

Engineering of Synthetic Transcriptional Switches in Yeast

Transcriptional switches can be utilized for many purposes in synthetic biology, including the assembly of complex genetic circuits to achieve sophisticated cellular systems and the construction of biosensors for real-time monitoring of intracellular metabolite concentrations. Although to date such switches have mainly been developed in prokaryotes, those for eukaryotes are increasingly being reported as both rational and random engineering technologies mature. In this review, we describe yeast transcriptional switches with different modes of action and how to alter their properties. We also discuss directed evolution technologies for the rapid and robust construction of yeast transcriptional switches.

The ChpR transcriptional regulator of Sinorhizobium meliloti senses 3,5,6-trichloropyridinol, a degradation product of the organophosphate pesticide chlorpyrifos

The global use of organophosphate insecticides (OPPs) and the growing concern of off-target side effects due to OPP exposure has prompted the need for sensitive and economical detection methods. Here we set out to engineer a previously identified OPP responsive transcription factor, ChpR, from Sinorhizobium melilotii to respond to alternative OPPs and generate a repertoire of whole-cell biosensors for OPPs. The ChpR transcription factor and cognate promoter P _chpA, have been shown to activate transcription in the presence of the OPP chlorpyrifos (CPF). Utilizing a GFP reporter regulated by ChpR in a whole-cell biosensor we found that the system responds significantly better to 3,5,6-trichloro-2-pyridinol (TCP), the main degradation product of CPF, compared to CPF itself. This biosensor was able to respond to TCP at 390 nM within 4 h compared to 50 µM of CPF in 7 h. The ChpR-P _chpA , and the activating ligand TCP, were able to regulate expression of a kanamycin resistance/sucrose sensitivity (kan/sacB) selection/counterselection module suitable for high throughput mutagenesis screening studies. The ability to control both GFP and the kan/sacB module demonstrates the utility of this reporter for the detection of CPF affected areas. The ChpR-P _chpA system serves as an additional positive regulator switch to add to the growing repertoire of controllers available within synthetic biology.