Specific detection of p-chlorobenzoic acid by Escherichia coli bearing a plasmid-borne fcbA'::lux fusion.

In this communication we report on a genetically engineered bacterium that reacts by light emission to the presence of 4-chlorobenzoic acid. To construct this strain, DNA fragment (1.7 kb) upstream from the 4-chlorobenzoic acid dehalogenase (fcb) operon of Arthrobacter SU was fused to Vibriofischeri luxCDABE genes. An Escherichia coli strain transformed with a multi-copy plasmid (pASU) bearing this fusion responded to the presence of 4-chlorobenzoic acid and a few closely related compounds by increased luminescence, exhibiting a high specificity but a relatively low sensitivity. While it could be somewhat, improved by manipulating the experimental pH, sensitivity remained too low for real time applicability. Nevertheless, the principle of using dehalogenase promoters as environmental pollution sensor was demonstrated.