title: Multiple mechanisms responsible for strong Congo-red-binding variants of Escherichia coli O157:H7 strains.
abstract: High variability in the expression of csgD-dependent, biofilm-forming and adhesive properties is common among Shiga toxin-producing Escherichia coli. Although many strains of serotype O157:H7 form little biofilm, conversion to stronger biofilm phenotypes has been observed. In this study, we screened different strains of serotype O157:H7 for the emergence of strong Congo-red (CR) affinity/biofilm-forming properties and investigated the underlying genetic mechanisms. Two major mechanisms which conferred stronger biofilm phenotypes were identified: mutations (insertion, deletion, single nucleotide change) in rcsB region and stx-prophage excision from the mlrA site. Restoration of the native mlrA gene (due to prophage excision) resulted in strong biofilm properties to all variants. Whereas RcsB mutants showed weaker CR affinity and biofilm properties, it provided more possibilities for phenotypic presentations through heterogenic sequence mutations.
authors.affiliation: Molecular Characterization of Foodborne Pathogens Research Unit, Eastern Regional Research Center, Agricultural Research Service, U. S. Department of Agriculture, Wyndmoor, PA 19038, USA chin-yi.chen@ars.usda.gov.
authors.forename: Chin-Yi
authors.initials: CY
authors.lastname: Chen
authors.affiliation: Molecular Characterization of Foodborne Pathogens Research Unit, Eastern Regional Research Center, Agricultural Research Service, U. S. Department of Agriculture, Wyndmoor, PA 19038, USA.
authors.forename: Ly-Huong T
authors.initials: LH
authors.lastname: Nguyen
authors.affiliation: Molecular Characterization of Foodborne Pathogens Research Unit, Eastern Regional Research Center, Agricultural Research Service, U. S. Department of Agriculture, Wyndmoor, PA 19038, USA.
authors.forename: Bryan J
authors.initials: BJ
authors.lastname: Cottrell
authors.affiliation: Molecular Characterization of Foodborne Pathogens Research Unit, Eastern Regional Research Center, Agricultural Research Service, U. S. Department of Agriculture, Wyndmoor, PA 19038, USA.
authors.forename: Peter L
authors.initials: PL
authors.lastname: Irwin
authors.affiliation: Molecular Characterization of Foodborne Pathogens Research Unit, Eastern Regional Research Center, Agricultural Research Service, U. S. Department of Agriculture, Wyndmoor, PA 19038, USA.
authors.forename: Gaylen A
authors.initials: GA
authors.lastname: Uhlich
mesh_terms: D000595:Amino Acid Sequence; D001435:Bacteriophages / Q000235:genetics; D018441:Biofilms; D003224:Congo Red / Q000378:metabolism*; D019453:Escherichia coli O157 / Q000145:classification / Q000302:isolation & purification / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000235:genetics; D023061:Gene Order; D005816:Genetic Complementation Test; D056426:Genetic Loci; D008969:Molecular Sequence Data; D010641:Phenotype; D011533:Proviruses / Q000235:genetics; D016415:Sequence Alignment; D016662:Virus Integration
chemical_list: D029968:Escherichia coli Proteins; C451279:MlrA protein, E coli; D003224:Congo Red
keywords: Congo red; O157:H7; STEC; biofilm; mlrA; rcsB