Program > Browse abstracts by speaker > Loot Céline

Integrons are genetic elements involved in bacterial adaptation. They contain an integrase and an array of gene cassettes whose expression decreases with distance from the beginning of the array. Stress activates the integrase leading to capture and shuffling of cassettes through site-specific recombination between attC and attI integron sites. The concomitant changes in cassette expression allow the exploration of diverse phenotypic combinations. Here we demonstrate that the integrase also catalyzes cassette integration into bacterial genomes outside of the known att integron sites. Once integrated, these cassettes can be expressed if located near bacterial promoters and can be excised at the integration point or outside, inducing chromosomal modifications in the latter case. Analysis of more than 5 × 105 independent integration events revealed a very large genomic integration landscape. We identified consensus recombination sequences, named attG sites, which differ greatly in sequence and structure from classical att sites. These results unveil an alternative route for dissemination of adaptive functions in bacteria and expand the role of integrons in bacterial evolution.