Inactivation of <i>brpA</i> by allelic exchange.

The gentamicin acetyl transferase gene was flanked by 1,000- and down-stream of brpA forming PflgB-gent, and brpA was displaced by allelic exchange (A). Deletion of brpA was confirmed by PCR analysis using primers located within gent and 1,000 bp downstream of the gene (A and B), primers within brpA (C), and flaB (D). Arrow heads (A) indicate the primer location and the expected amplicon size. Molecular masses are shown at the left of the gel.