The response of Escherichia coli to exposure to the biocide polyhexamethylene biguanide

School of Biosciences, Cardiff University, Museum Avenue, PO Box 911, Cardiff CF10 3US, UK Correspondence Andrew P. Morby morby{at}cardiff.ac.uk The global response of Escherichia coli to the broad-spectrum biocide polyhexamethylene biguanide (PHMB) was investigated using transcriptional profiling. The transcriptional analyses were validated by direct determination of the PHMB-tolerance phenotypes of derivatives of E. coli MG1655 carrying either insertionally inactivated genes and/or plasmids expressing the cognate open reading frames from a heterologous promoter in the corresponding chromosomally inactivated strains. The results showed that a wide range of genes was altered in transcriptional activity and that all of the corresponding knockout strains subsequently challenged with biocide were altered in tolerance. Of particular interest was the induction of the rhs genes and the implication of enzymes involved in the repair/binding of nucleic acids in the generation of tolerance, suggesting a novel dimension in the mechanism of action of PHMB based on its interaction with nucleic acids. Abbreviations: PHMB, polyhexamethylene biguanide Original macroarray data have been deposited at the NCBI Gene Expression Omnibus ( http://www.ncbi.nlm.nih.gov/projects/geo/index.cgi ), accession number GSE2827 . Present address: Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth PL1 3DH, UK.