STRUCTURAL ORGANIZATION OF VIRULENCE-ASSOCIATED PLASMIDS OF YERSINIA-PESTIS

The complete nucleotide sequence and gene organization of the three vi rulence plasmids from Yersinia pestis KIM5 were determined. Plasmid pP CP1 (9,610 bp) has a GC content of 45.3% and encodes two previously kn own virulence factors, an associated protein, and a single copy of IS1 00. Plasmid pCD1 (70,504 bp) has a GC content of 44.8%. It is known to encode a number of essential virulence determinants, regulatory funct ions, and a multiprotein secretory system comprising the low-calcium r esponse stimulation that is shared with the other two Yersinia species pathogenic for humans (Y. pseudotuberculosis and Y. enterocolitica). A new pseudogene, which occurs as an intact gene in the Y. enferocolit ica and Y. pseudotuberculosis-derived analogues, was found in pCD1. It corresponds to that encoding the lipoprotein YlpA. Several intact and partial insertion sequences and/or transposons were also found in pCD 1, as well as six putative structural genes with high homology to prot eins of unknown function in other yersiniae. The sequences of the gene s involved in the replication of pCD1 are highly homologous to those o f the cognate plasmids in Y. pseudotuberculosis and Y. enterocolitica, but their localization within the plasmid differs markedly from those of the latter. Plasmid pMT1 (100,984 bp) has a GC content of 50.2%. I t possesses two copies of IS100, which are located 25 kb apart and in opposite orientations. Adjacent to one of these IS100 inserts is a par tial copy of IS285. A single copy of an IS200-like element (recently n amed IS154I) was also located in pMT1. In addition to 5 previously des cribed genes, such as murine toxin, capsule antigen, capsule anchoring protein, etc., 30 homologues to genes of several bacterial species we re found in this plasmid, and another 44 open reading frames without h omology to any known or hypothetical protein in the databases were pre dicted.