Adaptation by Deletogenic Replication Slippage in a Nascent Symbiont

Area of Science:

• Microbial evolution
• Genomics
• Symbiosis

Background:

• Intracellular symbiotic bacteria undergo genome degeneration due to host association.
• The molecular mechanisms driving this genome degeneration are not well understood.

Purpose of the Study:

• To investigate the molecular mechanisms behind genome degeneration in symbiotic bacteria.
• To compare the genomes of Sodalis praecaptivus and Candidatus Sodalis pierantonius to understand evolutionary changes.

Main Methods:

• Comparative genomics of Sodalis praecaptivus and Candidatus Sodalis pierantonius.
• Characterization of indel mutations in Candidatus Sodalis pierantonius.

Main Results:

• Candidatus Sodalis pierantonius exhibits a high propensity for deletions caused by polymerase slippage in G+C-rich repetitive regions.
• This slippage-prone phenotype is linked to the loss of DNA recombination machinery components early in symbiosis.
• This mechanism facilitates rapid adaptation to the host environment, similar to bacterial mutator strains.

Conclusions:

• Loss of DNA repair mechanisms contributes to genome degeneration in symbiotic bacteria.
• Rapid deletions driven by polymerase slippage are a key mechanism for adaptation in newly established symbionts.
• This process mirrors the evolution of mutator strains in bacterial populations.