Detection of 4-chlorobenzoate using immobilized recombinant Escherichia coli reporter strains

A test for the detection of 4-chlorobenzoic acid (4-CBA) based on reporter microorganisms is developed. A 1.7-kb DNA fragment, upstream of the dehalog enase operon from Arthrobacter sp. strain SU, is fused to the promoterless luciferase operon of Vibrio fischeri. This reporter construct is introduced into two different Escherichia coil strains (UTL2 and RFM443), which speci fically respond to the presence of 4-CBA with Light emission. The developme nt and optimization of an alginate-based immobilization procedure of the mi croorganisms in microtiter plates is described. In this format, 4-CBA can b e detected in the concentration range of 113 muM-3.6 mM. The membrane leaky mutant UTL2 of E. coil transformed with the reporter construct improves th e detection limit to 28 muM when 150 mM KNO3 is added to the medium. (C) 20 00 Elsevier Science B.V. All rights reserved.