Cellulose modulates biofilm formation by counteracting curli-mediated colonization of solid surfaces in Escherichia coli.
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.
Gualdi
Luciana
L
Department of Biomolecular Sciences and Biotechnology, University of Milan, Via Celoria 26, 20133 Milan, Italy.
Tagliabue
Letizia
L
Department of Biomolecular Sciences and Biotechnology, University of Milan, Via Celoria 26, 20133 Milan, Italy.
Bertagnoli
Stefano
S
Department of Biomolecular Sciences and Biotechnology, University of Milan, Via Celoria 26, 20133 Milan, Italy.
Ieranò
Teresa
T
Department of Organic Chemistry and Biochemistry, University 'Federico II', Naples, Italy.
De Castro
Cristina
C
Department of Organic Chemistry and Biochemistry, University 'Federico II', Naples, Italy.
Landini
Paolo
P
Department of Biomolecular Sciences and Biotechnology, University of Milan, Via Celoria 26, 20133 Milan, Italy.
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*
C109182:CsgB protein, E coli; C499694:CsgD protein, E coli; D029968:Escherichia coli Proteins; D015534:Trans-Activators; C489688:csgA protein, E coli; D002482:Cellulose