Sediments are key players in the optimum functioning of ecosystems; however, they also represent the largest known repository of harmful contaminants. The vast variety of these sediment-associated contaminants may exert harmful effects on marine communities and can impair ecosystem functioning. Whole-cell biosensors are a rapid and biologically relevant tool for assessing environmental toxicity. Therefore, in this study, we developed a bioassay-based toxicity measurement system using genetically modified bacteria to create a whole-cell optical biosensor. Briefly, reporter bacteria were integrated and immobilized using a calcium alginate matrix on fiber-optic tips connected to a photon counter placed inside a light-proof, portable case. The calcium alginate matrix acts as a semi-permeable membrane that protects the reporter-encapsulated optical fiber tips and allows the inward passage of toxicant(s) to induce a dose-dependent response in the bioreporter. The samples were tested by directly submerging the fiber tip with immobilized bacteria into vials containing either water or suspended sediment samples, and the subsequent bioluminescent responses were acquired. In addition to bioavailable sediment toxicity assessments, conventional chemical methods, such as liquid chromatography–mass spectroscopy (LC-MS) and inductively coupled plasma optical emission spectroscopy (ICP-OES), were used for comprehensive evaluation. The results demonstrated the efficacy of the biosensor in detecting various toxicity levels corresponding to identified contaminants, highlighting its potential integration into environmental monitoring frameworks for enhanced sediment and water quality assessments. Despite its utility, this study notes the system’s operational challenges in field conditions, recommending future enhancements for improved portability and usability in remote locations.

Sediments are key players in the optimum functioning of ecosystems; however, they also represent the largest known repository of harmful contaminants. The vast variety of these sediment-associated contaminants may exert harmful effects on marine communities and can impair ecosystem functioning. Whole-cell biosensors are a rapid and one of the biologically relevant tools for assessing environmental toxicity. Therefore, in this study, we aimed to develop a bioassay-based toxicity measurement system using genetically modified bacteria to create a whole-cell optical biosensor. Briefly, reporter bacteria are integrated and immobilized using a calcium-alginate matrix on fiber-optic tips connected to a photon counter placed inside a light-proof, portable case. The calcium alginate matrix acts as a semi-permeable membrane that protects the reporter-encapsulated optical fiber tips and allows the inward passage of the toxicant(s) to induce a dose-dependent response in the bioreporter. Samples were tested by directly submerging the fiber tip with immobilized bacteria into vials containing either water or suspended sediment samples and the subsequent bioluminescent responses acquired. In addition to bioavailable sediment toxicity assessments, conventional chemical methods – liquid chromatography-mass spectroscopy (LC-MS), inductively coupled plasma optical emission spectroscopy (ICP-OES) for comprehensive evaluation were likewise used. Results demonstrated the biosensor's efficacy in detecting various toxicity levels corresponding to identified contaminants, showcasing its potential integration into environmental monitoring frameworks for enhanced sediment and water quality assessments. Despite its utility, the study notes the system's operational challenges in field conditions, recommending future enhancements for improved portability and usability in remote locations.

Wildfires that destroy residential infrastructure can generate chemically complex soil contamination; however, post-fire screening is often limited and does not directly reflect biological hazards. Herein, we integrated a multi-stress lux-based whole-cell bioreporter panel of genetically engineered Escherichia coli strains with non-targeted LC-MS profiling to obtain a mechanism-informed assessment of soils collected from a residential property impacted by the January 2025 Los Angeles wildfires. The bioreporter panel resolved heterogeneous and statistically significant stress signatures across the analyzed samples. In particular, extracts from U3–U5 produced selective suppression of the membrane and fatty acid biosynthesis bioreporters, along with reduced growth. In contrast, extract U5 induced a proteotoxic heat-shock response signature. In parallel, non-targeted LC-MS detected 1813 chemical features and enabled the putative annotation of a subset of signals consistent with combustion-derived organics and reactive electrophiles, providing a chemical context for the observed bioassay fingerprints. The integrated workflow provides mechanism-resolved hazard triage within 48 h, as implemented herein (24 h elutriate preparation plus up to 20 h microplate kinetics), supporting the prioritization of hotspots for confirmatory analysis, remediation, and risk assessment.

Sediment-associated contaminants pose persistent environmental risks, yet conventional sediment assessment workflows often require laboratory infrastructure and extensive sample preparation, limiting their suitability for rapid field monitoring. This study presents the development of a field-deployable instrument and a novel cuvette-based detection method for rapid effect-based sediment monitoring. Proteotoxic-stress-reporting Escherichia coli TV1061 cells were immobilized in a crosslinked alginate hydrogel at the bottom of standard cuvettes, thereby enabling direct contact with an overlying sediment layer while maintaining physical separation and a clear optical detection zone. The developed instrument enabled rapid sequential cuvette measurements under field conditions. An optimal incubation time (OIT) of 85 min was established. Measurements of sediment extracts showed good agreement with a conventional microplate reader assay (Pearson’s r = 0.977). Analytical characterization using ethanol showed a concentration-dependent response, with 0.75% (v/v), the lowest tested concentration, yielding a significant response on both the instrument and a conventional microplate reader. Direct analysis of unprocessed environmental sediments produced significant inhibition of the bioluminescent responses, and on-site measurements demonstrated the feasibility of operating the complete platform under field conditions. Overall, the platform provides a practical approach for rapid, on-site effect-based screening of environmental sediments while substantially simplifying sample preparation and biosensor operation.