Biofilm formation by and multicellular behavior of Escherichia coli O55:H7, an atypical enteropathogenic strain.
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.
Weiss-Muszkat
Michal
M
Food-Safety Research Unit, Department of Food Science, Agricultural Research Organization (ARO), The Volcani Center, P.O. Box 6, Beth-Dagan 50250, Israel.
Shakh
Dana
D
Zhou
Yizhou
Y
Pinto
Riky
R
Belausov
Eddy
E
Chapman
Matthew R
MR
Sela
Shlomo
S
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
D001426:Bacterial Proteins; C534546:CsgG protein, E coli; D004251:DNA Transposable Elements; D029968:Escherichia coli Proteins; D008074:Lipoproteins; C077481:Crl protein, Bacteria