Aggregative Adherence Fimbria I Expression in Enteroaggregative Escherichia coliRequires Two Unlinked Plasmid Regions. (Reannouncement with New Availability Information)

摘要

Adherence to HEp-2 cells by many enteroaggregative Escherchia coli (EAggEC)strains is associated with the expression of flexible, bundle-forming fimbriae 2 to 3 nm in diameter, designated aggregative adherence fimbriae I (AAF/1). We have previously reported the molecular cloning and TnphoA mutagenesis of AAF/I genes from the large plasmid of prototype EAggEC strain 17-2. Here, we report that further mapping and subcloning of AAF/I regions suggest that expression of the fimbriae requires two separate plasmid regions (designated regions I and 2). Approximately 9 kb of DNA unnecessary for fimbrial expression separates the two regions; this intervening segment encodes the EAggEC heat-stable enterotoxin (EAST1). Neither region was capable of conferring aggregative HEp-2 adherence (AA) when cloned individually; when the two regions were cloned as a single fragment or when each was cloned into a different vector and introduced into the same E. coli HBIO1 cell, AA was restored. AA-positive constructs also expressed human erythrocyte hemagglutination, autoagglutination in broth cultures, and the production of AAF/I as detected by immunogold electron microscopy.