The pCoo Plasmid of Enterotoxigenic Escherichia coli Is a Mosaic Cointegrate

Abstract

CS1 is the prototype of a class of pili of enterotoxigenic Escherichia coli (ETEC) associated with diarrheal disease in humans. The genes encoding this pilus are carried on a large plasmid, pCoo. We report the sequence of the complete 98,396-bp plasmid. Like many other virulence plasmids, pCoo is a mosaic consisting of regions derived from multiple sources. Complete and fragmented insertion sequences (IS) make up 24% of the total DNA and are scattered throughout the plasmid. The pCoo DNA between these IS elements has a wide range of G؉C content (35 to 57%), suggesting that these regions have different ancestries. We find that the pCoo plasmid is a cointegrate of two functional replicons, related to R64 and R100, which are joined at a 1,953-bp direct repeat of IS100. Recombination between these repeats in the cointegrate generates the two smaller replicons which coexist with the cointegrate in the culture. Both of the smaller replicons have plasmid stability genes as well as genes that may be important in pathogenesis. Examination by PCR of 17 other unrelated CS1 ETEC strains with a variety of serotypes demonstrated that all contained at least parts of both replicons of pCoo and that strains of the O6 genotype appear to contain a cointegrate very similar to pCoo. The results suggest that this family of CS1-encoding plasmids is evolving rapidly.

Pathogenomics of the Virulence Plasmids ofEscherichia coli

“…(124). The composite regions of pCoo are separated by IS100-associated direct repeats, suggesting that a recombination event occurring between regions of two different plasmids resulted in the formation of the cointegrate pCoo (62). The key feature identified on this plasmid was the polycistronic coo operon, which contains four genes encoding the CS1 pilus.…”

“…Some of the original designations have been replaced by newer nomenclature (i.e., CFA/III is CS8, and the PCF types have all been replaced by CS types), whereas others have retained their original names (i.e., CFA/I) (64). Plasmid pCoo was the first completely sequenced human ETEC CF-encoding plasmid (62). pCoo was isolated from human ETEC strain C921b-1, which is known to express CS1 and CS3 (143).…”

Evolution of the Chaperone/Usher Assembly Pathway: Fimbrial Classification Goes Greek

“…The CFA/I, CS1, CS2, CS4, CS5, CS14, CS17, CS19, and PCF071 antigens of human enterotoxigenic E. coli isolates are carried by plasmids (8,60,89,92,97,98,120,219,270,308,358). The presence of these fimbrial antigens in human isolates is thought to reflect their selective binding to human tissue (102).…”

Genomic characterization of asymptomatic Escherichia coli isolated from the neobladder

“…Nine features were identified that were exclusively present in both neobladder isolates (Table 5). All nine of these features are similar to those encoded on the ETEC plasmid pCOO (Froehlich et al, 2005). These genes are all from a type IV secretion apparatus known as the R64 thin pilus, which is utilized in liquid-based conjugations (Kim & Komano, 1997).…”

“…The hybridization patterns of the unique features of the neobladder isolates (Table 5) suggested that each isolate contained at least one plasmid. The genes shared only between the neobladder isolates are part of a type IV secretion system from the pCOO plasmid in ETEC (Froehlich et al, 2005). Other genes that are specific to each of the isolates (Tables 3 and 4) are also part of plasmid transfer or replication genes, suggesting that the core of the type IV system is similar but not identical between these two plasmids.…”