The prophage carrying bfp3 is capable of excision. Panel A. The Bfgi2 prophage (grey bar) is flanked by the B. fragilis 638R genome (black bar). The bfp3 gene (open white arrow), tRNAArg(white arrowhead) and genes flanking Bfgi2 (mid-grey) are shown. The attR and attL sequences (underlined) are shown in the expanded sequence. The locations of primers used in these studies are shown by small black arrows (see Table 4). Panel B. Agarose gel electrophoretic analysis of PCR reactions to test for excision of the prophage (Lane 2) and for the circular intermediate of the 'phage (Lane 3). Lane 1 contains DNA size markers. Panel C. Schematic representation of the 638R genome, after excision of the Bfgi2 element. Colour scheme is as for panel A. The regenerated attB site (underlined) is shown in the expanded sequence.