The Fish Pathogen "Candidatus Clavichlamydia salmonicola"-A Missing Link in the Evolution of Chlamydial Pathogens of Humans

Astrid Collingro (Corresponding author), Stephan Köstlbacher, Alexander Siegl, Elena R Toenshoff, Frederik Schulz, Susan O Mitchell, Thomas Weinmaier, Thomas Rattei, Duncan J Colquhoun, Matthias Horn

Publications: Contribution to journalArticlePeer Reviewed


Chlamydiae like Chlamydia trachomatis and Chlamydia psittaci are well-known human and animal pathogens. Yet, the chlamydiae are a much larger group of evolutionary ancient obligate intracellular bacteria that includes predominantly symbionts of protists and diverse animals. This makes them ideal model organisms to study evolutionary transitions from symbionts in microbial eukaryotes to pathogens of humans. To this end, comparative genome analysis has served as an important tool. Genome sequence data for many chlamydial lineages are, however, still lacking, hampering our understanding of their evolutionary history. Here, we determined the first high-quality draft genome sequence of the fish pathogen "Candidatus Clavichlamydia salmonicola", representing a separate genus within the human and animal pathogenic Chlamydiaceae. The "Ca. Clavichlamydia salmonicola" genome harbors genes that so far have been exclusively found in Chlamydia species suggesting that basic mechanisms important for the interaction with chordate hosts have evolved stepwise in the history of chlamydiae. Thus, the genome sequence of "Ca. Clavichlamydia salmonicola" allows to constrain candidate genes to further understand the evolution of chlamydial virulence mechanisms required to infect mammals.

Original languageEnglish
Article numberevad147
Number of pages12
JournalGenome Biology and Evolution
Issue number8
Publication statusPublished - 24 Aug 2023

Austrian Fields of Science 2012

  • 106026 Ecosystem research
  • 106022 Microbiology


  • Animals
  • Humans
  • Chlamydia/genetics
  • Fishes
  • Chordata
  • Chlamydiales/genetics
  • Eukaryota
  • Mammals
  • gene families
  • chlamydiae
  • Chlamydia trachomatis
  • Clavichlamydia
  • fish pathogen


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