GI-2 excision is promoted by the phage-related integrase gene. (A) Diagram of the excision intermediate showing the position of the 385-bp fragment carrying the recombined flanking GI-2 repeats (gray box), amplified by PCR with primers BAB1_1005F and BAB1_0983bR. (B) PCR detection of the 385-bp product amplified from the excision intermediate in weak acidic cultures of B. melitensis, B. suis, and B. abortus. M, 1-kb ladder (Roche). (C) Sequence alignment of the flanking att and attP sites. The 41-bp repeat is underlined. (D) Mutational analysis of the phage-related integrase. DNA from the B. abortus parental (2308 Nalr), mutant (int::Kmr), and complemented (int::Kmr/int) strains was used for PCR detection of the GI-2 scar (586 bp) and CI (385 bp).