Origin and evolution of the Bartonella Gene Transfer Agent
(English)Manuscript (preprint) (Other academic)
Gene transfer agents (GTAs) are bacteriophage particles that transfer bacterial DNA. Two GTAs have been identified in the Alphaproteobacteria: the RcGTA, which is widely distributed in a broad range of species; and the more recently evolved BaGTA, which is thought to have been important for the explosive radiation of the genus Bartonella. The BaGTA preferentially packages genes for host interaction factors amplified from an alternative, phage-derived origin of replication. Here, we show that the RcGTAs and the BaGTAs have non-overlapping phyletic distribution patterns in the Alphaproteobacteria. We identify BaGTA-like phage islands in Candidatus Tokpelaia hoelldoblerii, an early diverging lineage of Bartonella, as well as in three more distantly related alphaproteobacterial species. Moreover, we identify several BaGTA-like phage islands within the genus Bartonella, but unlike the BaGTA these are not conserved in either occurrence or genomic location. We thus hypothesize that the transfer of random DNA fragments with the aid of the GTA was an early innovation, which predated the amplification and targeted transfer of DNA segments flanking the phage-derived origin of replication. We propose a model for the gradual transformation of a prophage into a specialist GTA in a process driven by selection for transfer and recombination of host interaction factors within the bacterial population.
mobile elements, Phage domestication, GTA
Research subject Biology with specialization in Molecular Evolution
IdentifiersURN: urn:nbn:se:uu:diva-301779OAI: oai:DiVA.org:uu-301779DiVA: diva2:955250