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Preparation, Imaging, and Quantification of Bacterial Surface Motility Assays
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Repression of bacterial motility by a novel fimbrial gene product

X Li1, D A Rasko, C V Lockatell

  • 1Department of Microbiology and Immunology, University of Maryland School of Medicine and Veterans Affairs Medical Center, Baltimore, MA 21201, USA.

The EMBO Journal
|September 5, 2001
PubMed

Insights

Proteus mirabilis MrpJ protein represses flagella synthesis when mannose-resistant, Proteus-like (MR/P) fimbriae are produced, attenuating virulence. PapX from Escherichia coli is a functional homolog.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Urology

Background:

  • Proteus mirabilis is a significant uropathogen, particularly in catheterized patients.
  • Mannose-resistant, Proteus-like (MR/P) fimbriae and flagella are key virulence factors for P. mirabilis.
  • Urinary tract infections (UTIs) are common and can lead to severe complications.

Purpose of the Study:

  • To investigate the role of the mrpJ gene in P. mirabilis virulence.
  • To determine the regulatory relationship between MR/P fimbriae production and flagellar synthesis.
  • To identify potential functional homologs of MrpJ in other uropathogens.

Main Methods:

  • Transcriptional lacZ fusions and mutagenesis studies were employed to analyze gene regulation.
  • Electron microscopy was used to confirm flagellar synthesis.
  • Gel mobility shift assays were performed to assess protein-DNA interactions.
  • A murine model of ascending urinary tract infection was used to evaluate bacterial virulence.

Main Results:

  • The mrpJ gene product, MrpJ, represses transcription of the flagellar regulon.
  • Repression of flagella synthesis by MrpJ occurs when MR/P fimbriae are produced.
  • An mrpJ null mutant showed reduced virulence in a murine UTI model.
  • MrpJ does not directly bind to the flhDC operon regulatory region.
  • PapX from uropathogenic Escherichia coli was identified as a functional homolog of MrpJ.

Conclusions:

  • MrpJ acts as a negative regulator of flagellar synthesis in P. mirabilis, linking fimbrial production to motility.
  • This regulatory mechanism contributes to P. mirabilis virulence in the context of UTIs.
  • The identification of PapX as a homolog suggests conserved regulatory strategies among uropathogens.

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