Working at Molecular Characterization of Foodborne Pathogens Research Unit, Eastern Regional Research Center, Agricultural Research Service, United States Department of Agriculture, Wyndmoor, Pennsylvania, United States of America


Functional amyloid, in the form of adhesive fimbrial proteins termed curli, was first described in Salmonella and Escherichia coli. Curli fibers adhere to various host cells and structural proteins, interact with components of the host immune system, and participate in biofilm formation. Shiga toxin-producing E. coli (STEC) cause severe hemorrhagic diarrheal disease which can progress to hemolytic uremic syndrome in certain cases. STEC typically carrystx1, stx2, or both on lambdoidprophage. Although most STEC possess all of the genes required for functional curli production, curli expression is tightly regulated resulting in great variability in curli production among different STEC strains and serotypes. Curli and the exopolysaccharide cellulose are the major components of STEC biofilms. Both are controlled by the transcriptional regulator CsgD, whose expression is dependent on the RpoS sigma factor and enhanced by the MlrA transcription factor. We have shown that prophage insertions in the coding region of mlrA, often carrying anstxgene, are major barriers that limit csgD expression and curli production. This talk will discuss differences in csgD-dependent curli expression in various STEC serotypes and present new findings regarding prophage effects on mlrA expression and curli production.

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