Horizontal gene transfer of the Escherichia coli pap and prs pili operons as a mechanism for the development of tissue‐specific adhesive properties

Summary Escherichia coli strains bind to Galα1‐4Gal‐containing glycolipids via P pili‐associated G‐adhesins. Three functional classes of adhesins with different binding specificities are encoded by conserved G‐alleles. We suggest that the Class I papG‐allele of strain J96 is a novel acquisition possibly introduced via horizontal gene transfer into one of the two P pili gene clusters carried by this strain. Closely related strains in the ECOR collection of natural E. coli isolates carry either a Class II or a Class III G‐adhesin. Data indicate that genetic exchanges involving either entire pap or prs gene clusters or individual paplprs genes have occurred. We propose that the retention and spread of pap prs DNA among E. coli is the result of selection pressure exerted by mammalian intestinal isoreceptors.