Whole-Cell Fiber-Optic Biosensor for Real-Time, On-Site Sediment and Water Toxicity Assessment: Applications at Contaminated Sites Across Israel

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.