The contribution of vesicle-mediated DNA transfer to rapid adaptation

DA 1202/2-1

In large asexual populations most of the beneficial mutations are lost due to the combination of clonal interference and competition with multiple mutations. DNA transfer within the population allows for combinations of beneficial mutations that arose in independent lineages and can thereby accelerate the process of adaptation. Previous studies demonstrated that DNA transfer via conjugation and transformation has an important role in prokaryotic rapid adaptation. The contribution of DNA transfer to the adaptation rate was however different between the two transfer mechanisms. These differences suggest that the contribution of recombination to prokaryotic rapid adaptation may depend on the DNA transfer mechanism. In other words, differences in the DNA vehicle type and donor-recipient interaction mode may influence the recombination frequency and consequently also the adaptation dynamics. Here we propose to study the contribution of outer membrane vesicles to recombination and rapid adaptation in cyanobacteria. OMVs are secreted by many microbial species for various extracellular functions as well as intercellular communication. Accumulating evidence suggests that OMVs play an important role in DNA transfer within the population. Preliminary results from our laboratory reveal that OMVs are produced by freshwater cyanobacteria and they indeed contain nucleic acids. Our objectives include the characterization of OMV production dynamics and genetic content. In addition we will estimate OMVs transfer rate and efficiency within and across species boundaries. Using an experimental evolution setup, we aim to characterize the contribution of OMV-mediated transfer to selection sweeps and de novo allele introduction. Whole genome sequencing of the evolved strains from our experiment will enable us to characterize the contribution of OMVs-mediated transfer to cyanobacterial genetic variability and polymorphism. Our study is thus aimed to extend our knowledge of mechanisms for rapid adaptation in prokaryotes and their impact on genome evolution.

Publications

• Tanita Wein, Nils F. Hülter, Itzhak Mizrahi and Tal Dagan (2019) Emergence of plasmid stability under non-selective conditions maintains antibiotic resistance. Nature Communications, 10: 2595. DOI: 10.1038/s41467-019-10600-7