Transduction in microbial biosensors using multiplexed bioluminescence.

The enormous diversity of genetic responses in living microbes to their environment is an attractive resource on which to base biosensor designs. In particular, there is much interest in microbial sensors for environmental monitoring where toxicity can be ascertained directly by its action on cellular physiology. However, due to the complexities of living systems, the utility of genetic-based microbial sensors has been limited by the ability to accurately transduce the activities of specific genetic sensing systems into readily measurable signals. We present here a strategy for employing an additional signal in the sensor design, to provide an internal baseline control upon which to reliably interpret sensor responses. The strategy relies on using beetle luciferases capable of emitting optical signals of different wavelengths; the optical signals are a sensitive real-time indicator of genetic activity within the cells. The different wavelengths allow both a target and control signal to be incorporated into each cell, providing a means of differentiating between specific effects of a genetic sensing system and other non-specific interfering influences.