title: Biofilm formation by and multicellular behavior of Escherichia coli O55:H7, an atypical enteropathogenic strain.
abstract: Enteropathogenic Escherichia coli (EPEC) is an important causal agent of diarrheal illness throughout the world. Nevertheless, researchers have only recently begun to explore its capacity to form biofilms. Strain O55:H7 (DMS9) is a clinical isolate belonging to the atypical EPEC (aEPEC) group, which displays a high degree of genetic relatedness to enterohemorrhagic E. coli. Strain DMS9 formed a robust biofilm on an abiotic surface at 26 degrees C, but not at 37 degrees C. It also formed a dense pellicle at the air-liquid interface and developed a red, rough, and dry (RDAR) morphotype on Congo red agar. Unlike a previously described E. coli O157:H7 strain, the aEPEC strain seems to express cellulose. Transposon mutagenesis was used to identify biofilm-deficient mutants. One of the mutants was inactivated in the csgFG genes, required for assembly and secretion of curli fimbriae, while a second mutant had a mutation in crl, a thermosensitive global regulator that modulates sigma(S) activity and downstream expression of curli and cellulose. The two mutants were deficient in their biofilm formation capabilities and did not form a pellicle at the air-liquid interface. Unlike in Salmonella, the csgFG mutant in aEPEC completely lost the RDAR phenotype, while the crl mutant displayed a unique RDAR "pizza"-like morphotype. Genetic complementation of the two mutants resulted in restoration of the wild-type phenotype. This report is the first to describe and analyze a multicellular behavior in aEPEC and support a major role for curli and the crl regulator in biofilm development at low temperatures corresponding to the nonmammalian host environment.
authors.affiliation: Food-Safety Research Unit, Department of Food Science, Agricultural Research Organization (ARO), The Volcani Center, P.O. Box 6, Beth-Dagan 50250, Israel.
authors.forename: Michal
authors.initials: M
authors.lastname: Weiss-Muszkat
authors.forename: Dana
authors.initials: D
authors.lastname: Shakh
authors.forename: Yizhou
authors.initials: Y
authors.lastname: Zhou
authors.forename: Riky
authors.initials: R
authors.lastname: Pinto
authors.forename: Eddy
authors.initials: E
authors.lastname: Belausov
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Chapman
authors.forename: Shlomo
authors.initials: S
authors.lastname: Sela
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D018441:Biofilms / Q000254:growth & development*; D004251:DNA Transposable Elements; D054308:Enteropathogenic Escherichia coli / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000502:physiology*; D005816:Genetic Complementation Test; D006801:Humans; D008074:Lipoproteins / Q000235:genetics / Q000502:physiology*; D016254:Mutagenesis, Insertional; D013696:Temperature
chemical_list: D001426:Bacterial Proteins; C534546:CsgG protein, E coli; D004251:DNA Transposable Elements; D029968:Escherichia coli Proteins; D008074:Lipoproteins; C077481:Crl protein, Bacteria