ESCHERICHIA-COLI COLV PLASMID PRK100 - GENETIC ORGANIZATION, STABILITY AND CONJUGAL TRANSFER

Uropathogenic Escherichia coil strains express chromosomal and plasmid -encoded virulence-associated factors such as specific adhesins, toxin s and iron-uptake systems. A ColV plasmid (pRK100) of a uropathogenic strain and its host KS533 were studied. The host strain encodes the K1 capsule, and P and S fimbriae, but neither haemolysin nor the cytotox ic-necrotic factor CNF1, indicating that this strain does not harbour a larger pathogenicity island. A restriction map of pRK100 was constru cted on the basis of hybridization experiments and nucleotide sequenci ng. pRK100 harbours ColV, the conserved replication region RepFIB, the aerobactin-uptake system, a RepFIC replicon and additionally Colla as well as transposon Tn5431. The location of the RepFIC replicon was si milar to that in plasmid F. ColV plasmids and F thus share a region sp anning more than half the length of plasmid F. Even though their repli cation and transfer regions are homologous, ColV plasmids are found on ly in E. coil strains. Among the four other species tested, conjugal t ransfer of pRK100 was demonstrated, with low frequency, only to Klebsi ella pneumoniae, suggesting that a natural barrier effectively bars tr ansfer. In vitro stability of the plasmid with integration into the ch romosome to ensure maintenance in the presence of an incompatible plas mid was demonstrated.