Identification of new genes regulated by the marRAB operon in Escherichia coli

A study of the participation of non-marRAB chromosomal loci in chromosomal multiple antibiotic resistance (Mar) phenotype using TrophoA and TnlacZ elements helps study mar-sensitive fusions in a specially designed Escherichia coli recipient that has a temperature-sensitive plasmid carrying the mar locus and the mar RAB operon. Five mar-regulated gene fusions are detected, with beta-galactosidase expression being stimulated in two of them and alkaline phosphate expression being suppressed in the other three. Occurrence of these changes due to marA alone indicates that MarA is the regulatory protein that leads to enhanced resistance to multiple antibiotics.