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Neisseria meningitidis is structured in clades associated with restriction modification systems that modulate

Sonia Budroni1, Emilio Siena, Julie C Dunning Hotopp

  • 1Research Center, Novartis Vaccines and Diagnostics, 53100 Siena, Italy.

Proceedings of the National Academy of Sciences of the United States of America
|March 4, 2011
PubMed

Insights

Neisseria meningitidis (Nm) exhibits distinct phylogenetic clades shaped by gene acquisition and genomic remodeling. Clade-specific restriction modification systems likely drive this lineage structure and influence bacterial virulence.

Area of Science:

  • Microbiology
  • Genomics
  • Evolutionary Biology

Background:

  • Neisseria meningitidis (Nm) is a significant human pathogen with a complex population structure.
  • Previous studies using limited molecular data suggested distinct Nm lineages, but the evolutionary mechanisms and impact on pathogenicity remained unclear.
  • The high rate of recombination in Nm populations complicates understanding lineage evolution and persistence.

Purpose of the Study:

  • To investigate the population structure of Neisseria meningitidis using whole-genome sequencing.
  • To identify genomic features contributing to lineage diversification and their impact on virulence.
  • To elucidate the role of restriction modification systems in shaping Nm population structure and DNA exchange.

Main Methods:

  • Whole-genome sequencing of Neisseria meningitidis strains.
  • Phylogenetic analysis to determine clade structure.
  • Identification and distribution analysis of genomic tracts, including restriction modification systems.
  • Assessment of gene conversion lengths within and between clades.

Main Results:

  • Neisseria meningitidis is structured into distinct phylogenetic clades, each with unique genomic tracts acquired and remodeled.
  • High rates of recombination persist across the Nm chromosome, but gene conversion is longer within clades.
  • Twenty-two restriction modification systems were identified, distributed according to clade structure, suggesting horizontal gene transfer.
  • These systems create differential barriers to DNA exchange, consistent with the observed population structure.

Conclusions:

  • Genomic remodeling and clade-specific restriction modification systems are key drivers of lineage structure in Neisseria meningitidis.
  • These findings provide insights into the evolution of virulence in recombining bacterial populations.
  • The study offers an evolutionary framework applicable to other bacterial species with complex population dynamics.

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