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Pneumolysin localizes to the cell wall of Streptococcus pneumoniae

Katherine E Price1, Andrew Camilli

  • 1Howard Hughes Medical Institute and Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts 02111, USA.

Journal of Bacteriology
|January 27, 2009
PubMed

Insights

Streptococcus pneumoniae releases active pneumolysin (Ply) into the cell wall during growth, independent of cell lysis. This finding clarifies Ply

Area of Science:

  • Microbiology
  • Bacterial Pathogenesis
  • Molecular Biology

Background:

  • Streptococcus pneumoniae causes severe diseases like pneumonia and meningitis.
  • Pneumolysin (Ply) is a key virulence factor but its release mechanism is unclear.
  • Unlike other toxins, Ply lacks a signal peptide for secretion.

Purpose of the Study:

  • To investigate the localization and release mechanism of pneumolysin (Ply) from Streptococcus pneumoniae.
  • To determine if Ply is released during non-lytic growth.
  • To assess the activity and accessibility of cell wall-localized Ply.

Main Methods:

  • Cell fractionation and Western blotting were used to determine Ply localization.
  • Hemolytic assays were performed to assess Ply activity.
  • Extracellular protease accessibility and detergent release assays were conducted.

Main Results:

  • Exported Ply was primarily localized to the cell wall in 18 S. pneumoniae serotypes.
  • Ply localization occurred without detectable cell lysis during in vitro growth.
  • Cell wall-localized Ply demonstrated hemolytic activity and was accessible to protease and detergent.

Conclusions:

  • Pneumolysin is exported to the cell wall compartment during Streptococcus pneumoniae growth via a non-lytic mechanism.
  • Cell wall-localized Ply is active and accessible, suggesting a novel role in pathogenesis.
  • This finding challenges previous hypotheses regarding Ply release solely through autolysis.

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