Simultaneous quantification of the fluorescent responses of an ensemble of bacterial sensors.

Bacterial bioreporters are genetically engineered microbial strains capable of detecting specific chemicals, groups of chemicals or global biological effects such as toxicity or genotoxicity. A scheme for simultaneous selective detection of the fluorescent signals emitted by a bacterial biosensor array, able to detect four different types of toxicants, using a single photodetector (photomultiplier) is presented. The underlying principle of the scheme is to convert the spatially distributed signals from all the elements in the array to temporally distributed frequency multiplexed signals at the output of the photodetector. Experimental proof of this concept is demonstrated in a four-channel system, in which low power (a few tens of picowatts) fluorescent signals produced by the bacterial sensors are measured, while maintaining a wide dynamic range of detection (more than 3 orders of magnitude). Simultaneous monitoring of concentrations down to a few mg/l of different chemicals in a liquid sample is demonstrated.