title: Comprehensive mutagenesis of the fimS promoter regulatory switch reveals novel regulation of type 1 pili in uropathogenic Escherichia coli.
abstract: Type 1 pili (T1P) are major virulence factors for uropathogenic Escherichia coli (UPEC), which cause both acute and recurrent urinary tract infections. T1P expression therefore is of direct relevance for disease. T1P are phase variable (both piliated and nonpiliated bacteria exist in a clonal population) and are controlled by an invertible DNA switch (fimS), which contains the promoter for the fim operon encoding T1P. Inversion of fimS is stochastic but may be biased by environmental conditions and other signals that ultimately converge at fimS itself. Previous studies of fimS sequences important for T1P phase variation have focused on laboratory-adapted E coli strains and have been limited in the number of mutations or by alteration of the fimS genomic context. We surmounted these limitations by using saturating genomic mutagenesis of fimS coupled with accurate sequencing to detect both mutations and phase status simultaneously. In addition to the sequences known to be important for biasing fimS inversion, our method also identifies a previously unknown pair of 5' UTR inverted repeats that act by altering the relative fimA levels to control phase variation. Thus we have uncovered an additional layer of T1P regulation potentially impacting virulence and the coordinate expression of multiple pilus systems.
authors.affiliation: Infectious Diseases Group, Genome Institute of Singapore, Singapore 138672;
authors.forename: Huibin
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Stem Cell and Development, Genome Institute of Singapore, Singapore 138672;
authors.forename: Teodorus T
authors.initials: TT
authors.lastname: Susanto
authors.affiliation: Stem Cell and Development, Genome Institute of Singapore, Singapore 138672;
authors.forename: Yue
authors.initials: Y
authors.lastname: Wan
authors.affiliation: Infectious Diseases Group, Genome Institute of Singapore, Singapore 138672; Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 119074 slchen@gis.a-star.edu.sg.
authors.forename: Swaine L
authors.identifier: http://orcid.org/0000-0002-0107-2861
authors.initials: SL
authors.lastname: Chen
mesh_terms: D004926:Escherichia coli / Q000235:genetics* / Q000472:pathogenicity; D029968:Escherichia coli Proteins / Q000235:genetics*; D010861:Fimbriae, Bacterial / Q000235:genetics*; D016296:Mutagenesis; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics; D001743:Urinary Bladder / Q000382:microbiology*
chemical_list: D029968:Escherichia coli Proteins; D012333:RNA, Messenger
keywords: fimS; phase variation; saturating chromosomal mutagenesis; type 1 pili; urinary tract infection