Prophage-like gene transfer agents promote Caulobacter crescentus survival and DNA repair during stationary phase

Abstract

<jats:p>Gene transfer agents (GTAs) are prophage-like entities found in many bacterial genomes that cannot propagate themselves and instead package approximately 5 to 15 kbp fragments of the host genome that can then be transferred to related recipient cells. Although suggested to facilitate horizontal gene transfer (HGT) in the wild, no clear physiological role for GTAs has been elucidated. Here, we demonstrate that the α-proteobacterium <jats:italic>Caulobacter crescentus</jats:italic> produces bona fide GTAs. The production of <jats:italic>Caulobacter</jats:italic> GTAs is tightly regulated by a newly identified transcription factor, RogA, that represses <jats:italic>gafYZ</jats:italic>, the direct activators of GTA synthesis. Cells lacking <jats:italic>rogA</jats:italic> or expressing <jats:italic>gafYZ</jats:italic> produce GTAs harboring approximately 8.3 kbp fragment of the genome that can, after cell lysis, be transferred into recipient cells. Notably, we find that GTAs promote the survival of <jats:italic>Caulobacter</jats:italic> in stationary phase and following DNA damage by providing recipient cells a template for homologous recombination-based repair. This function may be broadly conserved in other GTA-producing organisms and explain the prevalence of this unusual HGT mechanism.</jats:p>