Improvement of an E. coli bioreporter for monitoring trace amounts of phenol by deletion of the inducible σ54-dependent promoter

An Escherichia coli bioreporter harboring the phenol-inducible mphK promoter (P-mphk) from Acinetobacter calcoaceticus PHEA-2 fused to a beta-galactosidase gene (lacZ) and the regulator gene (mopR) of A. calcoaceticus NCIB8250 was constructed to detect phenol. P-mphk containing three inverted repeats (IR1, IR2 and IR3) upstream of mphK was activated by the regulator MopR in the presence of phenol. Deletion analysis of P-mphk revealed that IR2 and IR3 were essential for promoter activity, while IR1 was involved in transcriptional repression. The sensitivity of the bioreporter for the detection of phenol (0.1-5 mu M) was improved by about 100% through deletion of IR1 in P-mphk.