Effects of local transcription and H‐NS on inversion of the fim switch of Escherichia coli

• Published in: Molecular microbiology 2000-04, Vol.36 (2), p.457-466
• Main Authors: O′gara, James P., Dorman, Charles J.
• Format: Article
• Language: English
• Subjects: Alleles; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Base Sequence; DNA-Binding Proteins - genetics; DNA-Binding Proteins - metabolism; Escherichia coli; Escherichia coli - genetics; Escherichia coli - growth & development; Escherichia coli - metabolism; Escherichia coli Proteins; FimB protein; Fimbriae, Bacterial - genetics; Fimbriae, Bacterial - metabolism; FimE protein; Gene Expression Regulation, Bacterial; Integrases - genetics; Integrases - metabolism; Molecular Sequence Data; Mutagenesis, Site-Directed; Promoter Regions, Genetic - genetics; recombinase; Recombination, Genetic; Repressor Proteins; Sequence Analysis, DNA; Transcription, Genetic
• ISSN: 0950-382X; 1365-2958
• DOI: 10.1046/j.1365-2958.2000.01864.x

The fim switch of Escherichia coli is responsible for phase‐variable expression of type 1 fimbriae. Switching in the ON‐to‐OFF and OFF‐to‐ON directions is promoted by the FimB recombinase, while the FimE recombinase directs switching predominantly in the ON‐to‐OFF direction. The effects of local promoter activity and the H‐NS nucleoid‐associated protein on inversion of the switch were assessed. In contrast to FimB‐mediated inversion, inversion of the switch by the FimE recombinase was unaffected by the H‐NS status of the cell. Transcription towards the switch from within a translationally inactivated fimE gene was found to bias the switch strongly in the OFF direction, creating a FimE+‐like phenotype in the absence of the FimE protein. This biasing was H‐NS dependent and was also contingent on transcription from within the switch. These data show that local transcription and a nucleoid‐associated protein both contribute to the modulation of a site‐specific recombination event on the bacterial chromosome.