The integrase of genomic island GI mediates the mobilization of GI and IS-related element CR2- unit through site-specific recombination.

In the worldwide health threat posed by antibiotic-resistant bacterial pathogens, mobile genetic elements (MGEs) play a critical role in favoring the dissemination of resistance genes. Among them, the genomic island GI and the IS-related element CR2 unit are believed to participate in this dissemination. However, the mobility of the two elements has not yet been demonstrated. Here, we found that the GI and CR2 units can excise from the host chromosomal attachment site () in . Through establishing a two-plasmid mobilization system composed of a donor plasmid bearing the GI and a trap plasmid harboring the in -deficient , we reveal that the integrase of GI can perform the excision and integration of GI and CR2 unit by site-specific recombination between core sites. Furthermore, we demonstrate that the integrase and the sites are required for mobility through knockout experiments. Our findings provide the first experimental characterization of the mobility of GI and CR2 units mediated by integrase. They also suggest a potential and unappreciated role of the GI integrase family in the dissemination of CR2 units carrying various resistance determinants in between.