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BIOFILM EXTRACELLULAR MATRIX IN ESCHERICHIA COLI

Matrix production in Escherichia coli

Bacterial growth on a surface often involves the production of a polysaccharide-rich extracellular matrix that provides structural support for the formation of biofilm communities. In this study, we have investigated cellulose and biofilm formation in a collection of E. coli isolates. We show that cellulose synthesis is the primary cause for biofilm formation and for the expression of the multicellular behavior (rdar morphotype) in the commensal E. coli strain 1094. In this strain, cellulose synthesis does not require CsgD nor AdrA, which is indicative of an alternative CsgD-independent cellulose regulatory pathway. We identified the genetic determinant involved in this pathway and provided evidence of the existence of alternative cellulose regulatory networks in E. coli and possibly in other cellulose-producing Enterobacteriaceae.

Da Re, S. and Ghigo, J. M. (2006) A CsgD-Independent Pathway for Cellulose Production and Biofilm Formation in Escherichia coli J Bacteriol.188:3073-87.

Localization of cellulose production in Escherichia coli

In the commensal Escherichia coli 1094 as in other Enterobacteriaceae, cellulose production relies on the expression of bacterial cellulose synthesis (Bcs) proteins and their post-translational activation upon binding of cyclic di-guanosine mono-phosphate second messenger (c-di-GMP) produced by diguanylate cyclases. c-di-GMP is a small diffusible molecule, therefore the large number of genes coding for DGC in most bacterial genomes raised the challenging question of control of functional specificity of c-di-GMP responses. Two genes of unknown function, uhjR and yhjQ, are located upstream of the bcs genes. We showed that yhjQ, but not yhjR, is essential for cellulose biosynthesis and we investigated the potential functional bases of the sequence homologies between MinD and yhjQ. We demonstrated that yhjQ displays a polar localization and that cell-to-cell adhesion is initiated through production of cellulose at yhjQ-labeled pole. Although we did not detect stable cell localization for the other Bcs proteins, our study support the notion that yhjQ-dependent subcellular localization of some elements of the cellulose machinery is required in E. coli and possibly other Enterobacteriaceae. This suggests that YhjQ, renamed BcsQ, could be a pole-localized cellular adaptor, which could be a general principle in cellulose and possibly other matrix exopolysaccharide polymer secretion.

• Le Quéré, B and J.M. Ghigo (2009) ‘BcsQ is an essential component of the Escherichia coli cellulose biosynthesis apparatus that localizes at the bacterial cell pole.’ Molecular Microbiology 72(3) :724 – 740..


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BIOFILM EXTRACELLULAR MATRIX IN SALMONELLA

Identification of a biofilm matrix associated protein in Salmonella enterica serovar Enteritidis

In this study realized in a collaboration led by Inigo Lasa’s laboratory (Pamplona, Spain), we demonstrated that the protein encoded by the gene stm2689 is required for air–liquid interface pellicle and biofilm formation. We also provided evidence that Stm2689, renamed BapA, (for Biofilm Associated Protein A), due to significant similarities with the Staphylococcus aureus Bap protein, plays a role in colonization of the murine intestine and subsequent organ invasion. The presence of surface proteins exhibiting homology with the Bap protein of S. aureus seems therefore widespread among diverse bacterial species. This suggests that the Bap proteins are required for an important and conserved function in bacterial biofilm development.

• Latasa,C. Roux, A. Toledo-Arana, A. ; Ghigo, J.M. ;Gamazo, C. Penadés, J. and I.Lasa (2005) BapA, a large secreted protein required for biofilm formation and host colonization of Salmonella enterica serovar Enteritidis Mol Microbiol. 58 :1322-1340

see also • Lasa I, Penades JR. (2005) Bap: A family of surface proteins involved in biofilm formation. Res Microbiol.157(2):99-107.

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Matrix production in Salmonella

The extracellular matrix is a salient characteristic of bacterial biofilms . Although still largely undefined, the presence of large amount of polysaccharides of different nature has been demonstrated in several bacteria . In Salmonella, I. Lasa laboratory with whom we have a close collaboration showed that cellulose is a major component of the extracellular biofilm matrix. See also pioneer work by Ute Römling laboratory.

Solano, C., Garcia, B., Valle, J., Berasain, C., Ghigo, J.M., Gamazo, C. and Lasa, I. (2002). “Genetic analysis of Salmonella enteritidis biofilm formation: critical role of cellulose.” Mol Microbiol 43(3): 793-80.