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Putative virulence factors are released in association with membrane vesicles from Burkholderia cepacia

Nick D Allan1, Cora Kooi, Pamela A Sokol

  • 1Canadian Bacterial Disease Network--National Centre of Excellence, Department of Microbiology, College of Biological Science, University of Guelph, ON.

Canadian Journal of Microbiology
|December 10, 2003
PubMed

Insights

Burkholderia cepacia releases membrane vesicles (n-MVs) containing virulence factors. These n-MVs may aid in delivering factors to tissues, potentially facilitating infection by this Gram-negative bacterium.

Area of Science:

  • Microbiology
  • Bacterial Pathogenesis
  • Molecular Biology

Background:

  • Gram-negative bacteria, including Burkholderia cepacia, release outer membrane vesicles (n-MVs) during growth.
  • These n-MVs can carry proteins and other molecules involved in bacterial interactions and pathogenicity.
  • Understanding the composition and function of n-MVs is crucial for deciphering bacterial virulence mechanisms.

Purpose of the Study:

  • To isolate and characterize native membrane vesicles (n-MVs) from clinical isolates of Burkholderia cepacia genomovars IIIa and V.
  • To compare the characteristics of n-MVs obtained through traditional methods versus a refined sucrose gradient technique.
  • To identify virulence factors and enzymes associated with B. cepacia n-MVs and elucidate their potential role in pathogenicity.

Main Methods:

  • Isolation of n-MVs from B. cepacia clinical isolates using filtration and differential centrifugation.
  • Characterization of n-MVs via electron microscopy to determine size, morphology, and bilayer structure.
  • Analysis of n-MV protein and enzyme content using virulence factor assays and peptidoglycan zymogram analysis.
  • Application of a linear isopycnic sucrose gradient for improved n-MV isolation and characterization.

Main Results:

  • Electron microscopy confirmed spherical, bilayered n-MVs ranging from 30-220 nm in diameter.
  • Associated virulence factors included lipase, phospholipase-N, and protease (metalloprotease).
  • Peptidoglycan zymogram analysis identified peptidoglycan-degrading enzymes (26, 28, 36, 66 kDa).
  • The sucrose gradient method yielded n-MVs with specific outer membrane and periplasmic proteins and lipopolysaccharide with a minor O-side chain, reducing flagella and pili contamination.

Conclusions:

  • Burkholderia cepacia selectively incorporates specific proteins and lipopolysaccharides into its n-MVs.
  • The presence of virulence factors and enzymes on n-MVs suggests a role in pathogenicity.
  • n-MVs may serve as a mechanism for delivering effector molecules to host tissues, contributing to B. cepacia infections.

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