Figure 3.

Schematic representation of the conjugation–recombination assay used for the integron cassette integration reaction. Briefly, the donor cell expresses the Π protein, encoded by pir and required for pAttC replication. This strain also provides the transfer functions necessary for its conjugation. The recipient is devoid of a pir gene and therefore cannot sustain pAttC replication. The recipient also contains a plasmid carrying the attI1 site (pSU38-attI1) and expresses IntI1 (symbolized by green ovals). Core site sequences in the attC and attI1 sites are represented as empty boxes, and correspond to those of Figure 1; red and pink ovals indicate the oriT; de novo synthesized strands are shown in blue. The relaxosome, which cleaves and pumps DNA into the recipient, is shown in yellow, and the donor and recipient cell walls and membranes are shown as gray vertical lines. The donor is represented with a pale yellow background.