Complete DNA sequence and structural analysis of the enteropathogenic Escherichia coli adherence factor plasmid

The complete nucleotide sequence and organization of the. enteropathogenic Escherichia coli (EPEC) adherence factor (EAP) plasmid of EPEC strain B171 (O111:NM) were determined, The EAF plasmid encodes two known virulence-rela ted operons, the bfp operon, which is composed of genes necessary for biosy nthesis of bundle-forming pill, and the bfpTVW (perABC) operon, composed of regulatory genes required for bfp transcription and also for transcription al activation of the eae gene in the LEE pathogenicity island on the EPEC c hromosome, The 69-kb EAF plasmid, henceforth designated pB171, contains, be sides the bfp and bfpTVW (perABC) operons, potential virulence-associated g enes, plasmid replication and maintenance genes, and many insertion sequenc e elements. Of the newly identified open reading frames (ORFs), two which c omprise a single operon had the potential to encode proteins with high simi larity to a C-terminal region of ToxB whose coding sequence is located on p O157, a large plasmid harbored by enterohemorrhagic E. coli, Another ORF, l ocated between the bfp and bfpTVW operons, showed high similarity with trcA , a bfpT-regulated chaperone-like protein gene of EPEC, Two sites were foun d to be putative replication regions: one similar to RepFIIA of p307 or F, and the other similar to RepFIB of R100 (NR1), In addition, we identified a third region that contains plasmid maintenance genes. Insertion elements w ere scattered throughout the plasmid, indicating the mosaic nature of the E AF plasmid and suggesting evolutionary events by which virulence genes may have been obtained.