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Identification of MrpI as the sole recombinase that regulates the phase variation of MR/P fimbria, a bladder colonization factor of uropathogenic Proteus mirabilis
Author(s) -
Li Xin,
Lockatell C. Virginia,
Johnson David E.,
Mobley Harry L. T.
Publication year - 2002
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.2002.03067.x
Subject(s) - proteus mirabilis , biology , fimbria , phase variation , recombinase , microbiology and biotechnology , mutant , operon , pilus , escherichia coli , genetics , phenotype , gene , recombination
Summary Proteus mirabilisis a common cause of urinary tract infection (UTI) in individuals with structural abnormalities or long‐term catheterization. The expression of mannose‐resistant/Proteus‐like (MR/P) fimbria is phase variable because of the inversion of a 251 bp DNA fragment that carries the promoter for themrpoperon. Previous studies have shown thatmrpI, which is transcribed divergently from themrpoperon, encodes a recombinase capable of switching the orientation of this invertible element. In this study, we constructed isogenicmrpInull mutants from a clinical isolate ofP. mirabilis, HI4320. A polymerase chain reaction (PCR)‐based invertible element assay revealed that the isogenicmrpInull mutants were locked in one phase, either expressing (locked on) MR/P fimbriae or not (locked off), which indicated that MrpI was the sole recombinase that regulated the phase variation of MR/P fimbria. The locked‐on and locked‐off mutants were evaluated for virulence in the CBA mouse model of ascending UTI by co‐challenges with each other and with the wild‐type strain. Results from these experiments demonstrated conclusively that the MR/P fimbria was a critical bladder colonization factor of uropathogenicP. mirabilis and also suggested that the ability to switch off the expression of MR/P fimbria might be important for kidney colonization.