Plasmid maps and construction. Plasmid pTn4001-RVC1 was constructed by replacing the pac gene of pMiniTn4001PsPuro with tetM from plasmid pSRT2 (A). Plasmid pMiniHimar1BSC1 contains a mini transposon incorporating pac conferring resistance to puromycin and the wild-type Himar1 transposase downstream of the Tn4001 native promoter sequence (B). In the pMHWT-2 plasmid, the pac in pMiniHimar1BSC1 has been replaced with tetM from pSRT2 (C). In plasmid pMHWT-1, the promoter sequence of the M. hyopneumoniae strain 232 P97 gene has been placed upstream of the wild-type Himar1 gene (D). In pMHC9-1, the wild-type Himar1 gene has been replaced with the hyperactive C9 mutant version of the gene (E).