Figure 1.

Restriction map of the rpoN locus and derived plasmids. The top line shows a map of the chromosomal rpoN locus and its neighbors. The closed box drawn on this line denotes the extent of the predicted rpoN ORF, and the two open boxes show the location of ORF1 and ORF2 upstream and downstream of rpoN that are evident in the sequence. The heavy dashed line above the ORFs indicates the extent of the sequence deposited in GenBank. Restriction fragments that were used in this study are shown below the map of the chromosomal locus in the corresponding positions and with the plasmids that carry them. A BamHI–SalI subfragment of pIMK200 which was used as the probe for rpoN is indicated as a hatched box. The ORFs disrupted by insertion of a tetracycline resistance (Tc^R) gene in plasmids pIMK208/210/267/268 (deleting an 81-bp BamHI fragment) and pIMK266 (deleting a 64-bp Tth111I–BspEI fragment) are indicated by the closed and open boxes as noted above. A, ApaI; B, BamHI; Bs, BspEI; N, NcoI; S, SmaI; Sa, Sau3AI; Sl, SalI; T, Tth111I.