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OmpA of a septicemic Escherichia coli O78--secretion and convergent evolution

Uri Gophna1, Diana Ideses, Ran Rosen

  • 1Department of Molecular Microbiology and Biotechnology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel.

International Journal of Medical Microbiology : IJMM
|December 15, 2004
PubMed

Insights

Outer membrane protein A (OmpA) from septicemic E. coli strains shows conserved loops in invasive bacteria. Secreted OmpA may protect bacteria from neutrophil elastase (NE) by competitive inhibition.

Area of Science:

  • Microbiology
  • Immunology
  • Molecular Biology

Background:

  • Outer membrane protein A (OmpA) is crucial for Gram-negative bacteria, mediating host interactions and immune responses.
  • Neutrophil elastase (NE) exerts bactericidal effects partly through OmpA degradation.
  • E. coli strains causing meningitis utilize OmpA to cross the blood-brain barrier.

Purpose of the Study:

  • To investigate the OmpA structure and secretion in septicemic E. coli 078 strains.
  • To explore the role of secreted OmpA in bacterial defense against host immune factors like NE.

Main Methods:

  • Analysis of OmpA structure in septicemic E. coli 078 strains.
  • Investigation of OmpA secretion in different growth phases.
  • Experimental validation of OmpA's protective role against NE.

Main Results:

  • Two surface-exposed loops of OmpA are conserved in invasive E. coli and other pathogenic Enterobacteriaceae, suggesting convergent evolution.
  • Significant quantities of OmpA are secreted in vesicles and soluble forms throughout bacterial growth.
  • Exogenous OmpA addition reduced bacterial killing by NE, supporting a protective role.

Conclusions:

  • Conserved OmpA loops indicate selective pressure in pathogenic Enterobacteriaceae.
  • Secreted OmpA may function as a decoy to protect bacteria from NE-mediated killing.
  • OmpA's dual role in host interaction and immune evasion is highlighted.

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