title: Putative virulence factors are released in association with membrane vesicles from Burkholderia cepacia.
abstract: 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.
authors.affiliation: Canadian Bacterial Disease Network--National Centre of Excellence, Department of Microbiology, College of Biological Science, University of Guelph, ON.
authors.forename: Nick D
authors.initials: ND
authors.lastname: Allan
authors.forename: Cora
authors.initials: C
authors.lastname: Kooi
authors.forename: Pamela A
authors.initials: PA
authors.lastname: Sokol
authors.forename: Terry J
authors.initials: TJ
authors.lastname: Beveridge
mesh_terms: D019121:Burkholderia Infections / Q000382:microbiology; D016956:Burkholderia cepacia / Q000145:classification / Q000235:genetics / Q000472:pathogenicity*; D002462:Cell Membrane / Q000201:enzymology* / Q000378:metabolism / Q000648:ultrastructure; D002500:Centrifugation, Isopycnic; D006801:Humans; D008049:Lipase / Q000378:metabolism; D008854:Microscopy, Electron; D012697:Serine Endopeptidases / Q000378:metabolism; D010738:Type C Phospholipases / Q000378:metabolism; D014774:Virulence; D037521:Virulence Factors / Q000378:metabolism*
chemical_list: D037521:Virulence Factors; D008049:Lipase; D010738:Type C Phospholipases; D012697:Serine Endopeptidases; C032923:microbial serine proteinases