DNA-SEQUENCING AND ANALYSIS OF THE LOW-CA2-RESPONSE PLASMID PCD1 OF YERSINIA-PESTIS KIM5()

The low-Ca2+-response (LCR) plasmid pCD1 of the plague agent Yersinia pestis KIM5 was sequenced and analyzed for its genetic structure. pCD1 (70,509 bp) has an IncFIIA-like replicon and a SopABC-like partition region. We have assigned 60 apparently intact open reading frames (ORF s) that are not contained within transposable elements, Of these, 47 a re proven or possible members of the LCR, a major virulence property o f human-pathogenic Yersinia spp., that had been identified previously in one or more of Y. pestis or the enteropathogenic yersiniae Yersinia enterocolitica and Yersinia pseudotuberculosis. Of these 47 LCR-relat ed ORFs, 35 constitute a continuous LCR cluster. The other LCR-related ORFs are interspersed among three intact insertion sequence (IS) elem ents (IS100 and two new IS elements, IS1616 and IS1617) and numerous d efective or partial transposable elements. Regional variations in perc ent GC content and among ORFs encoding effector proteins of the LCR ar e additional evidence of a complex history for this plasmid. Our analy sis suggested the possible addition of a new Syc- and Yop-encoding ope ron to the LCR-related pCD1 genes and gave no support for the existenc e of YopL. YadA likely is not expressed, as was the case for Y. pestis EV76, and the gene for the lipoprotein YlpA found in Y. enterocolitic a likely is a pseudogene in Y. pestis. The yopM gene is longer than pr eviously thought (by a sequence encoding two leucine-rich repeats), th e ORF upstream of ypkA-yopJ is discussed as a potential Syc gene, and a previously undescribed ORF downstream of yopE was identified as bein g potentially significant, Eight other ORFs not associated with IS ele ments were identified and deserve future investigation into their func tions.