BIOTRANSFORMATION OF 2,4-DINITROTOLUENE BY ESCHERICHIA COLI: PATHWAY DESCRIPTION AND APPLICATION FOR LANDMINE DETECTION

Current methods for the detection of buried landmines, mostly based on the use of hand-held metal detectors, are hazardous and inefficient. 2,4-dinitrotoluene (DNT), a volatile impurity in military grade explosives, is a potential tracer for the detection of TNT-based landmines and other buried military ordnance, and is therefore targeted by certain novel landmine stand-off detection systems. An Escherichia coli-based bioreporter for the detection of buried explosives, based on DNT and TNT detection, has recently been designed and constructed in our laboratory. The design is based on a fusion between the promoter of the yqjF gene, a predicted quinol oxidase, and a reporting element. Prior studies showed this bioreporter is not induced directly by DNT, rather by an unknown DNT metabolite.

The mechanism by which this bacterium utilizes DNT has not been identified thus far, nor were the direct inducing metabolite(s) and the regulatory mechanism which induces yqjF. This study aimed to characterize the biotransformation of DNT in E. coli, and to identify a DNT metabolite which is the direct inducer of the above mentioned bioreporter.

Liquid Chromatography Mass Spectrometry (LC/MS) was applied in order to identify the main metabolic products of DNT degradation in E. coli. Metabolic products characteristic of a reductive DNT biotransformation process, such as 4-hydroxylamino-2-nitrotoluene (4HA2NT), 4-amino-2-nitrotoluene (4A2NT) and 2,4-diaminotoluene (DAT) were identified. Accordingly, a putative degradation pathway is presented. Our candidate for the direct inducer is 4HA2NT; when the yqjF bioreporter was exposed to this compound, specifically synthesized for this study, an immediate response was elicited.