Widespread recombination throughout Wolbachia genomes.

Area of Science:

• Microbial genetics
• Bacterial evolution
• Endosymbiont genomics

Background:

• Homologous recombination is a key driver of genetic variability in bacteria.
• Wolbachia are obligate intracellular endosymbionts found in many arthropods.
• Understanding recombination in Wolbachia is crucial for their phylogeny and adaptation.

Purpose of the Study:

• To investigate the extent and patterns of homologous recombination within and between housekeeping genes of Wolbachia.
• To determine if recombination contributes to genetic diversity in endosymbiotic Wolbachia strains.
• To explore the implications of recombination for Wolbachia's evolutionary history and host interactions.

Main Methods:

• Sequencing of four housekeeping genes (gltA, dnaA, ftsZ, groEL) from 22 Wolbachia strains (supergroups A and B).
• Phylogenetic inference and genetic variation analysis of gene sequences.
• Application of multiple recombination detection programs (MaxChi, Chimera, RDP, Geneconv).

Main Results:

• No or weak intragenic recombination was observed in ftsZ, dnaA, and groEL genes.
• Significant intragenic recombination, including horizontal DNA transfers, was detected in the gltA gene across divergent Wolbachia supergroups.
• Intergenic recombination was prevalent between all gene pairs, indicating extensive genome-wide exchange.

Conclusions:

• Wolbachia strains exhibit pervasive recombination, challenging previous assumptions about their genetic stability.
• Evidence suggests a chimeric origin for Wolbachia, shaped by frequent horizontal gene transfer.
• These findings have significant implications for understanding Wolbachia phylogeny, adaptation, and their role as endosymbionts in arthropods.