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

Can J Microbiol. 2003 Oct;49(10):613-24. doi: 10.1139/w03-078.


Like many other Gram-negative bacteria, Burkholderia cepacia naturally releases membrane vesicles (n-MVs) during normal growth. Through filtration and differential centrifugation, n-MVs from clinical isolates of the IIIa and V genomovars were isolated and their characteristics compared. Electron microscopy revealed that they were spherical, 30-220 nm in diameter, and bilayered. Virulence factors thought to play a role in pathogenicity (e.g., lipase, phospholipase-N, and protease, including a metalloprotease) were found associated with n-MVs, while peptidoglycan zymogram analysis also revealed 26, 28, 36, and 66 kDa peptidoglycan-degrading enzymes. n-MVs were often contaminated with flagella and pili when isolated by traditional methods, and a new strategy using a linear isopycnic sucrose gradient was utilized. For better characterization, this was applied to a representative genomovar IIIa strain (C5424) and showed that n-MVs consisted of a subset of specific outer membrane and periplasmic proteins as well as lipopoly saccharide possessing only a putative minor O-side chain polymer. This finding suggests that certain components are selected by B. cepacia during n-MV formation, and since some are putative virulence factors, this property could help deliver the factors to tissue, thereby aiding infection.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Burkholderia Infections / microbiology
  • Burkholderia cepacia / classification
  • Burkholderia cepacia / genetics
  • Burkholderia cepacia / pathogenicity*
  • Cell Membrane / enzymology*
  • Cell Membrane / metabolism
  • Cell Membrane / ultrastructure
  • Centrifugation, Isopycnic
  • Humans
  • Lipase / metabolism
  • Microscopy, Electron
  • Serine Endopeptidases / metabolism
  • Type C Phospholipases / metabolism
  • Virulence
  • Virulence Factors / metabolism*


  • Virulence Factors
  • Lipase
  • Type C Phospholipases
  • Serine Endopeptidases
  • microbial serine proteinases