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Applying Live Cell Imaging and Cryo-Electron Tomography to Resolve Spatiotemporal Features of the Legionella pneumophila Dot/Icm Secretion System
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The perplexing functions and surprising origins of Legionella pneumophila type IV secretion effectors

Irina S Franco1, Howard A Shuman, Xavier Charpentier

  • 1Department of Microbiology, Columbia University Medical Center, New York, NY 10032, USA.

Cellular Microbiology
|July 1, 2009
PubMed

Insights

Legionella pneumophila bacteria infect human macrophages, causing Legionnaires' disease. This pathogen evolved from protozoa, using effector proteins to survive within host cells.

Area of Science:

  • Microbiology
  • Cell Biology
  • Pathogenesis

Background:

  • Legionella pneumophila is a Gram-negative bacterium causing Legionnaires' disease, a severe pneumonia.
  • It infects and replicates within alveolar macrophages, key phagocytic immune cells.
  • Pathogens that evade macrophage destruction pose significant health challenges.

Purpose of the Study:

  • To understand the mechanisms by which L. pneumophila infects and survives within macrophages.
  • To explore the evolutionary origins of L. pneumophila's virulence factors.
  • To investigate how bacterial effector proteins manipulate host cell processes.

Main Methods:

  • Analysis of L. pneumophila's secretion system and effector proteins.
  • Investigation of host-pathogen interactions at the cellular level.
  • Comparative genomics to trace the origin of virulence genes.

Main Results:

  • L. pneumophila injects effector proteins into macrophages using a complex secretion system.
  • These effectors modify the phagosome, creating a specialized replication vacuole.
  • Evidence suggests effector genes are of protozoan origin, acquired through horizontal gene transfer.
  • This adaptation allows L. pneumophila to thrive within phagocytes.

Conclusions:

  • L. pneumophila has evolved into a professional phagocyte parasite, likely through adaptation in protozoan hosts.
  • Its virulence relies on sophisticated manipulation of host vesicular trafficking.
  • Understanding these mechanisms is crucial for combating Legionnaires' disease.

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