Abstract

The pigmentation (Pgm+) phenotype of Yersinia pestis includes a number of different characteristics which appear to be associated with a 102 kb segment of chromosomal DNA known as the pgm locus. In Y. pestis KIM6+, the pgm locus is flanked by direct copies of a repeated element that probably plays a role in the spontaneous deletion of this region. We have sequenced the ends of these elements and shown that they have features in common with bacterial insertion sequences. In addition we show that a clone, pSDR498, from the pgm locus of KIM6+ restores pesticin sensitivity and the iron-regulated expression of three polypeptides, 240 kDa, 190 kDa, and 68 kDa in size, to Pgm- cells. In vitro transcription/translation assays and Escherichia coli minicells were used to analyse the products encoded by various subclones of pSDR498. Pesticin sensitivity mapped to a 5.9 kb fragment that encodes a 68 kDa protein derived from a 72 kDa precursor. Synthesis of the 190 kDa protein was restored by a 19.2 kb clone, indicating that the structural gene for this protein also resides within the pgm locus of Y. pestis KIM6+. Finally, a survey of our Pgm- strains indicates that 97% have also deleted the sequences encoding the 190 kDa protein and pesticin sensitivity.