Quorum sensing negatively regulates multinucleate cell formation during intracellular growth of Burkholderia pseudomallei in macrophage-like cells

PLoS One. 2013 May 21;8(5):e63394. doi: 10.1371/journal.pone.0063394. Print 2013.

Abstract

Burkholderia pseudomallei is a Gram-negative environmental bacterium and the causative agent of melioidosis, a potentially fatal, acute or chronic disease endemic in the tropics. Acyl homoserine lactone (AHL)-mediated quorum sensing and signalling have been associated with virulence and biofilm formation in numerous bacterial pathogens. In the canonical acyl-homoserine lactone signalling paradigm, AHLs are detected by a response regulator. B. pseudomallei encodes three AHL synthases, encoded by bpsI1, bpsI2 and bpsI3, and five regulator genes. In this study, we mutated the B. pseudomallei AHL synthases individually and in double and triple combination. Five AHLs were detected and quantified by tandem liquid chromatography-mass spectroscopy. The major AHLs produced were N-octanoylhomoserine lactone and N-(3-hydroxy-decanoyl)homoserine lactone, the expression of which depended on bpsI1 and bpsI2, respectively. B. pseudomallei infection of macrophage cells causes cell fusion, leading to multinucleated cells (3 or more nuclei per cell). A triple mutant defective in production of all three AHL synthases was associated with a striking phenotype of massively enhanced host cellular fusion in macrophages. However, neither abrogation of host cell fusion, achieved by mutation of bimA or hcp1, nor enhancement of fusion altered intracellular replication of B. pseudomallei. Furthermore, when tested in murine models of acute melioidosis the AHL synthase mutants were not attenuated for virulence. Collectively, this study identifies important new aspects of the genetic basis of AHL synthesis in B. pseudomallei and the roles of these AHLs in systemic infection and in cell fusion in macrophages for this important human pathogen.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acyl-Butyrolactones / metabolism
  • Administration, Intranasal
  • Animals
  • Burkholderia pseudomallei / genetics
  • Burkholderia pseudomallei / growth & development*
  • Burkholderia pseudomallei / pathogenicity
  • Cell Line
  • Gene Deletion
  • Genes, Bacterial / genetics
  • Giant Cells / pathology*
  • Humans
  • Intracellular Space / microbiology*
  • Ligases / deficiency
  • Ligases / metabolism
  • Macrophages / microbiology*
  • Macrophages / pathology*
  • Melioidosis / microbiology
  • Melioidosis / pathology
  • Mice
  • Mice, Inbred BALB C
  • Quorum Sensing*
  • Virulence

Substances

  • Acyl-Butyrolactones
  • Ligases
  • N-acylhomoserine lactone synthase

Grants and funding

This work has been supported by the National Health and Medical Research Council and by Griffith University. GCU is supported by a Future Fellowship from the Australian Research Council. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.