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Updated: May 12, 2026

Forward Genetic Approaches in Chlamydia trachomatis
09:03

Forward Genetic Approaches in Chlamydia trachomatis

Published on: October 23, 2013

Comparative analysis of Chlamydia psittaci genomes reveals the recent emergence of a pathogenic lineage with a broad

Timothy D Read1, Sandeep J Joseph, Xavier Didelot

  • 1Division of Infectious Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, GA, USA.

Mbio
|March 28, 2013
PubMed

Insights

Chlamydia psittaci, a dangerous pathogen, undergoes frequent genetic recombination and host switching, unlike related Chlamydia species. This suggests psittacosis may be a recently emerged disease linked to bird trade.

Area of Science:

  • Microbiology
  • Genomics
  • Evolutionary Biology

Background:

  • Chlamydia psittaci is a virulent intracellular bacterium causing psittacosis in humans and animals.
  • Its potential as a bioweapon highlights its significance as a CDC biothreat agent.
  • Previous genomic studies revealed frequent recombination in Chlamydia trachomatis.

Purpose of the Study:

  • To investigate homologous recombination and evolutionary dynamics in Chlamydia psittaci.
  • To compare recombination frequencies between C. psittaci and C. trachomatis.

Main Methods:

  • Comparative genomics analysis of 20 C. psittaci genomes from diverse strains and hosts.
  • Genome annotation to identify the core genome.
  • Phylogenetic and molecular clock analyses to reconstruct evolutionary history and track recombination origins.

Main Results:

  • A core genome of 911 genes was identified across all analyzed C. psittaci strains.
  • C. psittaci exhibits more frequent host switching and recombination than C. trachomatis.
  • Evidence of genome-wide homologous recombination, whole-plasmid exchange, and DNA import from unsampled lineages was found.
  • Three ancestral populations were predicted, and a clonal epidemic expansion linked to South American bird traders was identified.

Conclusions:

  • C. psittaci possesses a dynamic genome shaped by frequent recombination and host jumps.
  • The findings suggest psittacosis is a recently emerged disease, possibly originating in New World parrots and spread through the bird trade.

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