title: Cellulose modulates biofilm formation by counteracting curli-mediated colonization of solid surfaces in Escherichia coli.
abstract: In enterobacteria, the CsgD protein activates production of two extracellular structures: thin aggregative fimbriae (curli) and cellulose. While curli fibres promote biofilm formation and cell aggregation, the evidence for a direct role of cellulose as an additional determinant for biofilm formation is not as straightforward. The MG1655 laboratory strain of Escherichia coli only produces limited amounts of curli and cellulose; however, ectopic csgD expression results in strong stimulation of curli and cellulose production. We show that, in a csgD-overexpressing derivative of MG1655, cellulose production negatively affects curli-mediated surface adhesion and cell aggregation, thus acting as a negative determinant for biofilm formation. Consistent with this observation, deletion of the bcsA gene, necessary for cellulose production, resulted in a significant increase in curli-dependent adhesion. We found that cellulose production increased tolerance to desiccation, suggesting that the function of cellulose might be related to resistance to environmental stresses rather than to biofilm formation. Production of the curli/cellulose network in enterobacteria typically takes place at low growth temperature (<32 degrees C), but not at 37 degrees C. We show that CsgD overexpression can overcome temperature-dependent control of the curli-encoding csgBA operon, but not of the cellulose-related adrA gene, suggesting very tight temperature control of cellulose production in E. coli MG1655.
authors.affiliation: Department of Biomolecular Sciences and Biotechnology, University of Milan, Via Celoria 26, 20133 Milan, Italy.
authors.forename: Luciana
authors.initials: L
authors.lastname: Gualdi
authors.affiliation: Department of Biomolecular Sciences and Biotechnology, University of Milan, Via Celoria 26, 20133 Milan, Italy.
authors.forename: Letizia
authors.initials: L
authors.lastname: Tagliabue
authors.affiliation: Department of Biomolecular Sciences and Biotechnology, University of Milan, Via Celoria 26, 20133 Milan, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Bertagnoli
authors.affiliation: Department of Organic Chemistry and Biochemistry, University 'Federico II', Naples, Italy.
authors.forename: Teresa
authors.initials: T
authors.lastname: Ieranò
authors.affiliation: Department of Organic Chemistry and Biochemistry, University 'Federico II', Naples, Italy.
authors.forename: Cristina
authors.initials: C
authors.lastname: De Castro
authors.affiliation: Department of Biomolecular Sciences and Biotechnology, University of Milan, Via Celoria 26, 20133 Milan, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Landini
mesh_terms: D001422:Bacterial Adhesion; D018441:Biofilms / Q000254:growth & development*; D002482:Cellulose / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D013696:Temperature; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*
chemical_list: C109182:CsgB protein, E coli; C499694:CsgD protein, E coli; D029968:Escherichia coli Proteins; D015534:Trans-Activators; C489688:csgA protein, E coli; D002482:Cellulose