FIG. 2.

Structures of plasmids pGB2, pAY1099, and pAY1105. The aadA gene is flanked by a pair of BspHI sites in each vector, and its translation initiates at an ATG codon within one of these sites. Also shown are unique sites within the polylinker of pGB2 derived from pUC8 and within the fragment of the lacZ gene carried by plasmids pAY1099 and pAY1105 derived from pLITMUS28 (New England Biolabs). The positions of the aadA gene from plasmid R100, the region from R100 including its origin of replication (ori) (also present in Salmonella plasmid pSC101), the region of the E. coli lac operon encoding the β-complementing fragment of LacZ, and the int and attP genes from myxophage Mx8 are indicated. Text files of the sequences of these plasmids and detailed notes on their construction are available by e-mail upon request.