Fiber-Optic-Based Biomonitoring of Benzene Derivatives by Recombinant E. coli Bearing Luciferase Gene-Fused TOL-Plasmid Immobilized on the Fiber-Optic End

TOL plasmid in Pseudomonas putida mt-2 has a series of genes for the degradation of xylene, toluene, and their derivatives to pyruvate and acetaldehyde (or propionaldehyde). Two operons, i.e., upper operon and meta operon, play indispensable roles for the digestion of xylene derivatives: When XylR protein recognizes xylene derivatives, another controlling gene, xylS, is activated, which results in the activation of meta operon. Therefore, we have constructed a fusion gene between TOL plasmid and the firefly luciferase gene under the control of XylR and the promoter of xylS gene; i.e., by using fusions of the meta operon with promotorless luciferase expression vector from firefly, we have constructed and tested biomonitors for benzene derivatives. Bioluminescence specified by Escherichia coli (pTSN316), carrying xylR and xylS promoters, Amp^r, and luc, was measured in either a benzene derivative-saturated or o-methylbenzyl alcohol-dissolved medium both in the case of cell suspension and in the case of immobilized cell form. The utility of the biosensing system for monitoring in chemical plant drainage was demonstrated with samples supplemented with benzene derivatives. The xylR-xylS promoter-lux fusion carried by pTSN316 responded to a benzene-related chemical in sample solutions. Immobilization of the transformed E. coli, at one end of fiber optic, bearing firefly luciferase gene fused to TOL plasmid, has been demonstrated to fabricate a luminescent remote biomonitoring device for the protection of environmental deterioration. Due to the luminescent detection, the detection limits for benzene-related aromatics that are recognized by a binding protein (XylR) were parts-per-million. We had already submitted a preliminary report concerning the possibility of environmental monitoring based on the above idea by using the transformed E. coli in a cell-suspended solution. This paper describes mainly a fiber-optic-based biomonitoring device for the protection of environmental deterioration.