Bioluminescent bacterial biosensor for large-scale field deployment

We describe a biosensing module in which live bacteria, genetically "tailored" to respond to the presence of a specific target material, constitute the core sensing element, reporting their response by bioluminescence. The module is constructed of two channels: an 'induced' channel that measures the bioluminescent light emitted by bacteria exposed to the inspected area, and a 'reference' channel that measures in parallel the bioluminescent light emitted spontaneously by bacteria of the same batch. This enables to overcome signal variations generated by different batches of bacteria, and due to varying environmental operating conditions. A special low-noise optoelectronic circuit was constructed to detect the bioluminescence emitted by the bacteria in both channels. The bacteria are encapsulated in polymer beads that also contain nutrients and water, enabling long-term maintenance-free operation. The beads are packaged in special cassettes at the bottom of the module, so that the induced channel cassette is in direct contact with the ground underneath the module, whereas the reference channel cassette is isolated from the ground. The module contains, in addition, a digital signal processing unit, and a wireless communication unit. The module is designed to operate outdoors as an autonomous network element designed for large scale in-situ deployment. The module described herein was developed for the detection of buried landmines, by sensing the presence of 2,4-dinitrotoluene (DNT) vapors released by the mine, accumulating in the ground above it. Detection of DNT in the sub-ppm range is demonstrated.