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 6C), but not at 37 6C. We show that CsgD overexpression can overcome temperature-dependent control of the curliencoding csgBA operon, but not of the cellulose-related adrA gene, suggesting very tight temperature control of cellulose production in E. coli MG1655.

The diguanylate cyclase YddV controls production of the exopolysaccharide poly-N-acetylglucosamine (PNAG) through regulation of the PNAG biosynthetic pgaABCD operon

“…2). In contrast, inactivation of genes responsible for either cellulose (DbcsA) or PNAG biosynthesis (DpgaA) did not affect the red phenotype of the parental strain, consistent with previous observations that in E. coli MG1655, CR binding mostly depends on curli production (Gualdi et al, 2008;Ma & Wood, 2009). Plasmid-driven expression of DGCs resulted in very different effects on colony phenotype on CR media: expression of the AdrA protein conferred a red phenotype upon the csgA mutant strain, but not upon the DcsgA DbcsA double mutant, consistent with its role as an activator of cellulose production (Zogaj et al, 2001;Antoniani et al, 2010).…”

“…Indeed, in curli-producing strains of E. coli, EPS overproduction can result in the loss of the red colony phenotype on CR medium, possibly due to shielding of curli fibres (Gualdi et al, 2008;Ma & Wood, 2009). To understand whether YddV-dependent loss of the red colony phenotype on CR medium could indeed be due to PNAG overproduction, we verified EPS production in the presence and absence of the pYddV plasmid by plating on agar medium supplemented with CF, a fluorescent dye able to bind EPS.…”

“…To test whether YddV-dependent activation of pgaABCD transcription is mediated by its DGC activity, we constructed a plasmid carrying a mutant yddV allele encoding a protein in which the amino acids in the GGDEF catalytic site were changed to GGAAF (YddV GGAAF ); this mutation results in loss of DGC activity (De et al, 2008;Antoniani et al, 2010; data not shown). Overexpression of the YddV GGAAF protein did not affect pgaA transcript levels in real-time PCR experiments (Fig.…”

Reduction of hexavalent cromium by Serratia marcecens immobilized on active carbon and their potencial use in bioremediation

“…These particular pili are similar to curli structures described by Olsen et al (1989). The Curli (Pili or Microfi brillar) seem to be an envelope structure of major importance for surface colonization (Gualdi et al 2008), because provides stability to the biofi lm, allowing strong hydrodynamic conditions support on prolonged culture or without interruption (Donlan & Costerton 2002).…”

Role of EDTA and CSE1034 in curli formation and biofilm eradication of Klebsiella pneumoniae: a comparison with other drugs

“…7 It has earlier been reported that curli fibers are a major factor in adhesion to surfaces and biofilm formation in many enterobacteria. 8 The increasing rate of the biofilm problem and its impact on antibiotic resistance triggered us to think a new means, which could disrupt the biofilm formation by inhibiting bacterial adhesion and curli formation. In view of the above-mentioned antibiotic resistance because of the bacterial biofilm, we introduced a nonantibiotic adjuvant EDTA along with b-lactam and b-lactamase inhibitor, which altogether termed as CSE1034, has the potential to break bacterial biofilms significantly.…”