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Using the Overlay Assay to Qualitatively Measure Bacterial Production of and Sensitivity to Pneumococcal Bacteriocins
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Using the Overlay Assay to Qualitatively Measure Bacterial Production of and Sensitivity to Pneumococcal Bacteriocins

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Bacteriocin activity of Streptococcus pneumoniae is controlled by the serine protease HtrA via posttranscriptional

Suzanne Dawid1, Michael E Sebert, Jeffrey N Weiser

  • 1Department of Pediatrics, The Children's Hospital of Philadelphia, Pennsylvania, USA. sdawid@umich.edu

Journal of Bacteriology
|December 24, 2008
PubMed

Insights

Streptococcus pneumoniae uses quorum sensing to regulate pneumocin MN production. Opaque variants control this bacteriocin via HtrA protease, impacting colonization.

Area of Science:

  • Microbiology
  • Bacterial Pathogenesis
  • Molecular Biology

Background:

  • Streptococcus pneumoniae exhibits distinct colony variants (opaque and transparent) with differing roles in infection.
  • The blp locus in S. pneumoniae encodes pneumocin MN, a bacteriocin involved in intraspecies competition.
  • Pneumocin MN production is regulated by quorum sensing, involving a two-component system and peptide pheromones.

Purpose of the Study:

  • To investigate the post-transcriptional regulation of the blp locus in pneumococcal opacity variants.
  • To elucidate the role of the CiaRH two-component system and HtrA protease in pneumocin MN production.
  • To understand how differential regulation impacts bacterial competition and colonization.

Main Methods:

  • Analysis of blpMNPO transcript levels in opaque and transparent variants.
  • Assay of pneumocin MN-mediated inhibitory activity.
  • Generation and characterization of mutants deficient in CiaH or HtrA.
  • Assessment of dose-response to synthetic peptide pheromones.

Main Results:

  • Opaque and transparent variants produce similar blpMNPO transcript levels but differ in pneumocin MN activity.
  • The CiaRH system regulates HtrA, which controls post-transcriptional blp locus expression.
  • Transparent mutants lacking CiaH or HtrA exhibit enhanced pneumocin MN inhibition and altered pheromone response.
  • HtrA protease activity influences pneumocin MN production and signaling.

Conclusions:

  • Pneumococcal opacity variants differentially regulate pneumocin MN production at the post-transcriptional level.
  • The CiaRH system and HtrA protease are key regulators of this differential expression.
  • HtrA is a pleiotropic regulator affecting pneumocin production, signaling, and competence.
  • Complex regulation allows strategic deployment of bacteriocins based on environmental benefit.

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