Whole-cell biosensors are sensing devices that typically use biofilm-dwelling microorganisms to detect specific physical or chemical aspects of environmental samples. Microbial detection produces a signal that is transformed into user accessible data which can be as simple as colour change on a paper strip or as complex as quantitative digital display. Whole-cells can be embedded on a transducer or used separately as part of a multi-step assay format. Both unmodified and genetically modified cells have been used in this way. Metabolic reporters are used to detect toxicity that inhibits cell metabolism while catabolic reporters can be used to detect specific contaminants. Biosensors can provide data on the bioavailability of contaminants and are very relevant to monitoring bioremediation. Several commercially available sensors have been developed and some of these have been widely tested and demonstrated to be effective at measuring environmental contaminants
