The Contribution of Genetic Recombination to CRISPR Array Evolution

摘要: CRISPR (clustered regularly interspaced short palindromic repeats) is a microbial immune system against foreign DNA. Recognition sequences (spacers) encoded within the array mediate reaction in sequence-specific manner. The known mechanisms for evolution of arrays include spacer acquisition from DNA elements at time invasion and erosion through deletion. Here, we consider contribution genetic recombination between homologous to repertoire. Acquisition spacers exogenic via may confer recipient with immunity unencountered antagonists. For this purpose, develop novel method detection by modeling order multiple strains same species. Because evolutionary signal be similar that pervasive deletions or independent acquisition, our entails robustness analysis inference statistical comparison resampled perturbed data sets. We analyze sets four bacterial species: two Gammaproteobacteria species harboring type I Streptococcus II loci. find Escherichia coli agalactiae can explained solely vertical inheritance differential In Pseudomonas aeruginosa, an excess single potentially incorporated into locus during events. thermophilus, evidence present 5 out 70 strains. Genetic has been proposed accelerate adaptation combining beneficial mutations arose lineages. However, most under study, shaped mainly loss rather than recombination. Since content characterized rapid turnover, it likely not improving phage resistance cannot detected resolution intraspecies comparisons.