Schematic of pTn loxP -iTol2kan and pTn lox511 -iTol2kan: The iTol2kan DNA cassette was inserted at the Asc I site in both pTnMarkerless2 and pTnlox511(B)markerless1 plasmids, in either orientation. Mixtures of plasmids containing both orientations of iTol2 kan in pTnMarkerless2, and pTnlox511(B)markerless1, were used for generating deletion libraries in BACs. Clones from the library represented both orientations of the iTol2kan in them. The vertical boxes marked R (pink) and L (green), adapted from reference , indicate the 70 bp inverted repeat ends of the Tn10 transposon. The genes coding for transposase and ampicillin (amp) resistance are located outside the 70 bp inverted repeat ends. The arrows, thick black and broken and not drawn to scale, represent sequences for loxP and lox511, respectively.