Analysis of the tellurite resistance determinant on the pNT3B derivative of the pTE53 plasmid from uropathogenic Escherichia coli

We have found and sequenced a significant part of the previously described tellurite resistance determinant on mini-Mu derivative pPR46, named pNT3B, originally cloned from a large conjugative plasmid pTE53, found in Escherichia coli. This plasmid contains genes essential for tellurite resistance, together with the protective region bearing genes terX, Y, W, and the conserved spacing region bearing several ORFs of unknown function. Computer analysis of obtained sequence revealed a close similarity to the formerly described ter operons found on the Serratia marcescens plasmid R478 and the chromosome of Escherichia coli O157:H7. This finding confirms the presence of a whole region on the large conjugative plasmid that pTE53 originated from a uropathogenic E. coli strain, and suggests its possible role in horizontal gene transfer, resulting in the development of new pathogenic E. coli strains.