Open AccessFimbrial phase variation in Escherichia coli: dependence on integration host factor and homologies with other site-specific recombinases
Author(s) -
Charles J. Dorman,
Christopher F. Higgins
Publication year - 1987
Publication title -
journal of bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.652
H-Index - 246
eISSN - 1067-8832
pISSN - 0021-9193
DOI - 10.1128/jb.169.8.3840-3843.1987
Subject(s) - phase variation , recombinase , biology , escherichia coli , operon , gene , genetics , lac operon , host factor , microbiology and biotechnology , recombination , virulence
Expression of fimA, the structural gene for type 1 fimbriae of Escherichia coli, is phase variable. Significant homologies were identified between the recombinases which control fimbrial phase variation, FimB and FimE, and the integrase class of site-specific recombinases. Normal expression of fimA was shown to require the integration host factor (IHF). Mutations in either the himA-or the himD (hip) gene, which encode the alpha and beta subunits of IHF, respectively, prevented phase variation and locked expression of fimA in either the "on" or "off" phase. In addition, both himA and himD lesions caused a sevenfold reduction in expression of a phi(fimA-lacZ) operon fusion in strains in which fimA was locked in the on phase. Thus, IHF plays a dual role in controlling fimA expression: it is required both for inversion of the fimA control region and for efficient expression from the fimA promoter. A mechanism by which IHF may exert control over fimA expression is discussed.