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A type IV secretion system contributes to intracellular survival and replication of Burkholderia cenocepacia

S Umadevi Sajjan1, Lisa A Carmody, Carlos F Gonzalez

  • 1Department of Pediatrics and Communicable Diseases, University of Michigan Medical School, Ann Arbor, MI 48109, USA.

Infection and Immunity
|October 1, 2008
PubMed

Insights

Burkholderia cenocepacia uses a type IV secretion system to evade immune cells, like macrophages and epithelial cells. This system is crucial for its survival and replication within host cells.

Area of Science:

  • Microbiology
  • Cell Biology
  • Immunology

Background:

  • Burkholderia cenocepacia is a significant respiratory pathogen in cystic fibrosis (CF) patients.
  • This bacterium is known to survive within host cells by evading the endosome-lysosome fusion pathway.

Purpose of the Study:

  • To investigate the role of a plasmid-encoded type IV secretion system (T4SS) in the intracellular survival and replication of B. cenocepacia.
  • To understand how B. cenocepacia is processed within professional and non-professional phagocytes.

Main Methods:

  • Comparison of wild-type B. cenocepacia (K56-2) and a T4SS mutant (LC101) in CF airway epithelial cells and macrophages.
  • Analysis of bacterial colocalization with endocytic pathway markers (early endosomes, lysosomes).
  • Assessment of bacterial replication and survival at 24 hours post-infection.

Main Results:

  • Both wild-type and mutant strains entered and replicated in host cells.
  • Significantly higher survival of wild-type bacteria compared to the mutant at 24 hours.
  • Mutant bacteria were more frequently targeted to lysosomal degradation, while wild-type bacteria trafficked to the endoplasmic reticulum for replication.

Conclusions:

  • A functional plasmid-encoded T4SS is essential for B. cenocepacia's intracellular survival and replication.
  • The T4SS facilitates escape from the endocytic pathway and promotes replication in the endoplasmic reticulum.
  • Intracellular processing of B. cenocepacia is consistent across different host cell types.

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