FIG 2.

Gonococcal transformation with pUNCH755-derived plasmids pVCU161 to pVCU172. The image shown demonstrates how transformation with a single plasmid construct can result in two distinct genotypes following allelic exchange. The downstream crossover location is constrained by selection with chloramphenicol, whereas the upstream crossover can occur anywhere in tbpA or the truncated tbpB gene. If the crossover occurs upstream of the tbpB deletion, as shown on the left, the result is a TbpB⁻ phenotype. Conversely, if the crossover occurs downstream of the deletion location, as shown on the right, the result is a TbpB⁺ phenotype.