FIG. 7.
Separation of spoIIIAG and spoIIIAH from P1spoIIIA: models of the Campbell-type integration of plasmids into the spoIIIA locus. (A) Model in which a nonreplicating circular plasmid carrying spoIIIAF integrates into the spoIIIA locus by a single homologous recombination event. A horizontal arrow indicates that transcription from P1spoIIIA proceeds uninterrupted through spoIIIAF, while spoIIIAG and spoIIIAH are transcribed from P2spoIIIA. (B) Model in which a nonreplicating circular plasmid carrying spoIIIAE integrates into the spoIIIA locus by a single homologous recombination event. A horizontal arrow indicates that transcription from P1spoIIIA is interrupted by plasmid sequences (wavy line) before entering spoIIIAF, resulting in a sporulation-defective phenotype. The intervening plasmid DNA is represented by a wavy line in both panels and is not to scale.