Functional characterizations of effector protein BipC, a type III secretion system protein, in Burkholderia pseudomallei pathogenesis

J Infect Dis. 2015 Mar 1;211(5):827-34. doi: 10.1093/infdis/jiu492. Epub 2014 Aug 26.


Objectives: The bsa locus of Burkholderia pseudomallei encodes several proteins that are components of the type III secretion system (TTSS). BipC was postulated as one of the TTSS-3 effector proteins, but its role in the pathogenesis of B. pseudomallei infection is not well understood. Thus, the aim of this study was to determine its role(s) in the virulence of B. pseudomallei pathogenesis.

Methods: A bipC TTSS-3-deficient strain of B. pseudomallei and complemented strains were generated to assess the role of BipC as a type III translocation apparatus. Human cell lines and a mouse model of melioidosis were used for in vitro and in vivo assays, respectively.

Results: A significant 2-fold reduction was demonstrated in the percentage of adherence, invasion, intracellular survival, and phagosomal escape of the bipC mutant. Interestingly, microscopic studies have shown that BipC was capable of delayed B. pseudomallei actin-based motility. The virulence of the mutant strain in a murine model of melioidosis demonstrated that the bipC mutant was less virulent, compared with the wild type.

Conclusion: The results suggested that BipC possesses virulence determinants that play significant roles in host cell invasion and immune evasion.

Keywords: BipC; Burkholderia pseudomallei; host cell invasion; type III secretion system; type III translocation apparatus; virulence.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bacterial Secretion Systems*
  • Burkholderia pseudomallei / genetics
  • Burkholderia pseudomallei / metabolism
  • Burkholderia pseudomallei / pathogenicity*
  • Cell Line
  • Disease Models, Animal
  • Gene Deletion
  • Genetic Complementation Test
  • Humans
  • Immune Evasion
  • Melioidosis / microbiology
  • Melioidosis / pathology
  • Membrane Transport Proteins / genetics
  • Membrane Transport Proteins / metabolism*
  • Mice, Inbred BALB C
  • Virulence
  • Virulence Factors / genetics
  • Virulence Factors / metabolism*


  • Bacterial Secretion Systems
  • Membrane Transport Proteins
  • Virulence Factors