FIG. 1.

Genetic organization of the Y. pestis Ybt operons. Arrows, putative promoters for the operons. Gene designations are given below the lines, while nucleotide numbers are shown above the lines. Numbering corresponds to that used for GenBank accession no. AF091251 (29). An expanded version of the irp1-irp2-ybtU-ybtT-ybtE operon is shown; irp1, irp2, and ybtE genes are not drawn to scale in the expanded version. The size and location of the ybtU and ybtT deletions are indicated on the expanded map.