FIGURE 8.

Organization of the integron and the process of capturing and exchanging the gene cassettes. The open arrow indicates the open reading frame and is colored based on its function: the antimicrobial resistance gene is in red or in magenta, the attC gene is in green, and the intI1 gene is in orange. The open box indicates the attI locus. The integron is organized as a functional platform including the intI1 gene and the attI locus and a cassette array assembled through the acquisition of gene cassettes structured with an open reading frame and an attC locus. Expression of the gene cassettes is dependent on the common promoter, Pc, and the level of expression depends on the distance from the Pc. The IntI1 integrase binds to the attC locus of the excised gene cassette to help circularize the cassette (Collis et al., 1993; Hall and Collis, 1995).