FIG. 2.

Schematic of the original and hybrid cassette arrays. The aadA8b cassette has arisen by homologous recombination between the aadA2 cassette (hatched) in a dfrA12-orfF-aadA2 cassette array (e.g., GenBank accession no. AF284063) and an aadA1 cassette (shaded) in another integron. Cassettes are represented as narrow open boxes with a larger box at one end representing the 59-base element and are shown to scale. × indicates the position of the crossover. The region (between positions 602 and 647) where recombination took place is indicated by a small filled box. The attI1 site is shown as a tall open box and defines the end of the 5′-CS (thick black line). The thin black line beyond the last cassette represents the 3′-CS sequence.