Complete DNA sequence of Yersinia enterocolitica serotype 0 : 8 low-calcium-response plasmid reveals a new virulence plasmid-associated replicon

The complete nucleotide sequence and organization of the Yersinia enterocol itica serotype 0;8 low-calcium-response (LCR) plasmid, pYVe8081, were deter mined, The 67,720-bp plasmid encoded ail the genes known to be part of the LCR stimulon except for ylpA. Eight of 13 intact open reading frames of unk nown function identified in pYVe8081 had homologues in Yersinia pestis plas mid pCD1 or in Y. enterocolitica serotype 0:9 plasmid pYVe227. A region of approximately 17 kbp showed no DNA identity to pCD1 or pYVe227 and containe d six potential new genes, a possible new replicon, and two intact insertio n sequence (IS) elements, One intact IS element, ISYen1, was a new IS belon ging to the IS256 family. Several vestigial IS elements appeared different from the IS distribution seen in the other LCR plasmids, The RepA proteins encoded by Y. enterocolitica serotype 0:8 pYVeWA and pYVe8081 were identica l. The putative pYVe8081 replicon showed significant homology to the IncL/M replicon of pMU407.1 but was only distantly related to the replicons of pC D1 and pYVe227, In contrast, the putative partitioning genes of pYVe8081 sh owed 97% DNA identity to the spy/sopABC loci of pCD1 and pYVe227, Sequence analysis suggests that Yersinia LCR plasmids are from a common ancestor but that Y, enterocolitica serotype 0:8 plasmid replicons may have evolved ind ependently via cointegrate formation following a transposition event, The c hange in replicon structure is predicted to change the incompatibility prop erties of Y. enterocolitica serotype 0:8 plasmids from those of Y. enteroco litica serotype 0:9 and Y. pestis LCR plasmids.