Fig. 3

Integration and excision of gene cassettes by site-specific recombination. Intl encoded by the intl gene in the integron catalyses recombination between the attl1 site of the integron and/or the attC site(s) of gene cassette(s) resulting in insertion or excision of a cassette. One or more noncassette resistance genes may be inserted at the position of the 3′-CS. Horizontal arrows indicate the opposite orientations of intI and cassette-borne genes