Improvement of an E. coli bioreporter for monitoring trace amounts of phenol by deletion of the inducible sigma54-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 microM) was improved by about 100% through deletion of IR1 in P(mphK).