Abstract
Genome mosaicism in temperate bacterial viruses (bacteriophages) is so great that it obscures their phylogeny at the genome level. However, the precise molecular processes underlying this mosaicism are unknown. Illegitimate recombination has been proposed, but homeologous recombination could also be at play. To test this, we have measured the efficiency of homeologous recombination between diverged oxa gene pairs inserted into λ. High yields of recombinants between 22% diverged genes have been obtained when the virus Red Gam pathway was active, and 100 fold less when the host Escherichia coli RecABCD pathway was active. The recombination editing proteins, MutS and UvrD, showed only marginal effects on λ recombination. Thus, escape from host editing contributes to the high proficiency of virus recombination. Moreover, our bioinformatics study suggests that homeologous recombination between similar lambdoid viruses has created part of their mosaicism. We therefore propose that the remarkable propensity of the λ-encoded Red and Gam proteins to recombine diverged DNA is effectively contributing to mosaicism, and more generally, that a correlation may exist between virus genome mosaicism and the presence of Red/Gam-like systems.
Highlights
Bacterial viruses are the most abundant and diverse life form and exhibit high levels of evolvability and adaptability [1]
Temperate bacterial viruses alternate between a dormant state, during which viral DNA remains integrated in the host genome, and a lytic state of phage multiplication
Using the well known Escherichia coli l virus as a paradigm, we show that such homeologous recombination is remarkably efficient
Summary
Bacterial viruses (bacteriophages) are the most abundant and diverse life form and exhibit high levels of evolvability and adaptability [1]. A particularity of temperate virus genome evolution is their extensive sequence mosaicism [3] due to exchange of DNA sequences, facilitated by the frequent encounter inside the same bacterial host, for example between an invasive and a resident virus [4,5]. In the case of fully sequenced lambdoid viruses isolated from enterobacteria, genomes are on average 50% identical, except for DNA sequence patches showing more than 90% identity. Exchange of sequence modules can be explained by homologous recombination involving flanking, short and conserved sequences shared by a subset of related viruses [9]. It is possible that some regions flanking the most similar shared sequences have undergone homeologous recombination, i.e. recombination between related but diverged DNA sequences [10]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
