Genetics of Biofilms Laboratory - URA CNRS 2172  


  HEADDr GHIGO Jean-Marc / jean-marc.ghigo@pasteur.fr
  MEMBERSDr Christophe BELOIN / Dr Lionel FERRIERES / Dr Steve BERNIER/ Dr Gaelle HEMERY / Dr Laetitia TRAVIER / Dr Aswhini CHAUHAN / Mr Benjamin LE QUéRé / Ms Chara KOREA / Ms Olaya RENDUELES / Ms Alicia DeFRANCESCO / Mrs Patricia LATOUR-LAMBERT
Mrs Yolande MEUNIER


  Annual Report

Biofilms are communities of microorganisms that develop on surfaces and express still under-explored specific biological properties such as a characteristic increased tolerance to biocides. The objectives of the studies undertaken in the laboratory are to identify bacterial factors involved in the formation of commensal and pathogenic Escherichia coli biofilms, with particular emphasis on biofilm-specific physiological properties and competitive bacterial interactions within mixed biofilms.

Characterization of biofilm-associated bacterial metabolism

Global transcriptome analyses comparing surface-attached to planktonic culture conditions revealed that biofilm lifestyle triggers extensive modifications in gene expression that are proposed to correspond to profound physiological changes. However, with the exception of increased antibiotic tolerance, very few bacterial functions have yet been characterized as restricted to the biofilm lifestyle. In this study, we identified valine accumulation in the biofilm matrix as a metabolic response associated with biofilm formation. Beyond the biological significance of in biofilm valine secretion in many enterobacteriacae, our results experimentally support the hypothesis that metabolites can be more particularly secreted within certain biofilm conditions. Further identification of such metabolic signatures may allow the development of new markers to monitor or control the biofilm lifestyle.

•Valle, J.,Da Re, S., Schmid, S., Skurnik, D., D'Ari, R. and Ghigo, J. M. (2008) The amino acid valine is secreted in continuous-flow bacterial biofilms. J Bacteriol.190:264-74.

Characterization of a new trimeric autotransporter adhesins in uropathogenic Escherichia coli

Although E. coli is one of the best-studied free-living organisms, analysis of its genome sequence shows that many of its genes are still not or poorly characterized. We recently identified several genes encoding putative autotransporter surface adhesins that could contribute to bacteria-surface interactions taking place during biofilm formation. As part of our effort to better understand the arsenal of adhesins used by E. coli to colonize the urinary tract and other human sites, we characterized a new trimeric AT adhesin (UpaG) from uropathogenic E. coli. Members of the trimeric AT adhesin family are important virulence factors for several Gram-negative pathogens and we demonstrated that UpaG is indeed able to promote biofilm formation on abiotic surfaces but also onto human bladder epithelial cells, via its affinity to fibronectin and laminin. Although the upaG gene is cryptic under most laboratory conditions, it has recently been found to be a promising ExPEC vaccine candidate, therefore suggesting it is expressed in vivo and we are currently trying to understand upaG regulation under in vitro and in vivo conditions.

•Valle, J., Mabbett, A. N., Ulett, G. C., Toledo-Arana, A., Wecker, K., Totsika, M., Schembri, M. A.,Ghigo, J. M. andBeloin, C. (2008) UpaG, a new member of the trimeric autotransporter family of adhesins in uropathogenic Escherichia coli ; J Bacteriol.190:4147-61.

A short-time-scale colloidal system reveals early bacterial adhesion dynamics

The investigation of key molecular events involved in biofilm formation demonstrated the role surface-exposed adhesins in this process. However, many questions remain regarding the mechanisms and biophysics of surface adhesion. In collaboration with biophysicist of the Institut Curie, we combined micrometric colloidal beads as adhesion substrates and flow cytometry analysis to develop a high-resolution analysis that reveals adhesin-dependent behavior in the very first steps of surface colonization by bacteria. We performed a quantitative real-time analysis of adhesion kinetics using several strains of the bacterium Escherichia coli, genetically engineered to produce well characterized cell surface adhesins known to promote biofilm development. We evidenced previously unknown adhesin-dependent behaviors, such as clear-cut differences in the very initial phases of surface colonization. We also demonstrated that initial adhesion correlates with almost instant surface property changes and that cell-to-cell association might serve as a surface colonization amplification mechanism. This study introduces an original approach to investigate the intricate relationships between the physico-chemistry of abiotic surfaces and bacterial adhesion.

• Beloin, C.; HouryA;, Froment , M. ; Ghigo J.M. and N. Henry. (2008). A short time scale colloidal system reveals early bacterial adhesion dynamics and  adhesin-dependent behaviours. PLoS Biology 6(7): e167

Keywords: Biofilm, Escherichia coli

Ggb.jpg

Figure Use of colloidal particles (left), fluorescent bacteria and flow cytometry (right) to study bacterial adhesion



  Publications

•Beloin, C.; Houry, A;, Froment , M. ;Ghigo J.M.and N. Henry. (2008).A short time scale colloidal system reveals early bacterial adhesion dynamics and adhesin-dependent behaviours.PLoS Biology6(7): e167

•Valle, J., Da Re, S., Schmid, S., Skurnik, D., D'Ari, R. andGhigo, J. M.(2008) The amino acid valine is secreted in continuous-flow bacterial biofilms J Bacteriol.190:264-74.

•Valle, J., Mabbett, A. N., Ulett, G. C., Toledo-Arana, A., Wecker, K., Totsika, M., Schembri, M. A.,Ghigo, J. M.and Beloin, C.(2008) UpaG, a new member of the trimeric autotransporter family of adhesins in uropathogenic Escherichia coli. J Bacteriol.190:4147-61.

•Valle, J., Da Re, S., Henry, N., Fontaine, T., Balestrino, D., Latour-Lambert, P.and Ghigo, J. M.(2006) Broad-spectrum biofilm inhibition by a secreted bacterial polysaccharide. Proc Natl Acad Sci U S A.103:12558-63.

• 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.



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Activity Reports 2009 - Institut Pasteur
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