Origin and Evolution of the Bartonella Gene Transfer Agent

Area of Science:

• Microbiology
• Genetics
• Evolutionary Biology

Background:

• Gene transfer agents (GTAs) are domesticated bacteriophages facilitating bacterial DNA transfer.
• Understanding GTA emergence mechanisms and selective forces remains limited.
• Two Alphaproteobacteria GTAs, RcGTA and BaGTA, differ in host range and DNA packaging.

Purpose of the Study:

• To compare BaGTA genes with homologous bacteriophage genes in Bartonella species.
• To elucidate the evolutionary pathway of BaGTAs from prophages.
• To propose a model for prophage transformation into DNA-amplifying GTAs.

Main Methods:

• Comparative genomic analysis of BaGTA and homologous prophage genes.
• Phylogenetic inferences and substitution frequency analyses.
• Examination of genomic organization and flanking regions.

Main Results:

• BaGTA genes show codivergence with the host genome, unlike prophages with multiple integration events.
• Prophage genes are not universally present and lack consistent genomic insertion sites.
• Genomic rearrangements near BaGTA disrupt normal phage replication and gene expression coordination.

Conclusions:

• Prophages can evolve into GTAs that transfer amplified bacterial DNA segments.
• Codivergence with the host genome is a key factor in BaGTA evolution.
• Genomic rearrangements play a role in GTA functional divergence from ancestral phages.