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Uncovering the link between the SpnIII restriction modification system and LuxS in Streptococcus pneumoniae

Hannah N Agnew1, John M Atack2,3, Ann R D Fernando1

  • 1Research Centre for Infectious Diseases, Department of Molecular and Biomedical Science, University of Adelaide, Adelaide, SA, Australia.

Frontiers in Cellular and Infection Microbiology
|May 17, 2023
PubMed

Insights

Streptococcus pneumoniae switches DNA methylation patterns affecting virulence. The spnIII system and luxS gene interact, influencing bacterial adaptation to different host environments like nasopharynx and bloodstream.

Area of Science:

  • Microbiology
  • Genetics
  • Bacterial Pathogenesis

Background:

  • Streptococcus pneumoniae exhibits DNA methylation pattern switching via the spnIII locus, creating subpopulations (A-F).
  • Specific spnIII alleles, like spnIIIB, correlate with increased nasopharyngeal carriage and reduced luxS gene expression.
  • The LuxS/AI-2 quorum sensing (QS) system is crucial for bacterial communication, virulence, and biofilm formation.

Purpose of the Study:

  • To investigate the interplay between spnIII alleles, luxS gene expression, and virulence in clinical Streptococcus pneumoniae isolates.
  • To understand how these regulatory networks influence bacterial adaptation to distinct host niches during infection.

Main Methods:

  • Analysis of two clinical Streptococcus pneumoniae isolates from a pediatric meningitis patient (blood and CSF).
  • Assessment of virulence profiles in murine models.
  • Examination of spnIII system dynamics and luxS gene expression in strains recovered from infected murine nasopharynx.
  • Phenotypic comparison of wildtype strains with luxS-deleted mutants.

Main Results:

  • Clinical isolates displayed varying virulence profiles in mice.
  • SpnIII alleles switched in strains recovered from the murine nasopharynx, correlating with the isolate's origin.
  • The blood isolate showed high spnIIIB expression, linked to lower LuxS production.
  • Strains with deleted luxS exhibited altered phenotypes, resembling nasopharyngeal isolates.

Conclusions:

  • A regulatory network exists between the luxS gene and the type 1 restriction-modification system (spnIII) in Streptococcus pneumoniae.
  • This network plays a significant role in pneumococcal infections.
  • The system facilitates adaptation to specific host niches, impacting disease dynamics.
Keywords:
Quorum sensingStreptococcus pneumoniae (pneumococcus)biofilmclinical isolates bacterialvirulence

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