IBBS conference: Antimicrobial Strategies for Biofilm Control location:Winchester, UK date:10-11 september 2012
To study the gene expression and regulation in Salmonella biofilms, we constructed a library of 81 different GFP-promoter fusions of important S. Typhimurium biofilm genes, based on literature and in-house data. These include genes involved in biofilm regulation, matrix production, quorum sensing, metabolic genes and genes involved in motility and c-di-GMP synthesis and degradation. This library is currently being used to study the mode of action of biofilm inhibitors and to identify anti-biofilm targets.
For the mode of action studies, the effect of Salmonella biofilm inhibitors on the GFP expression is measured in time. As such we can quickly identify the effect of the compounds on specific biofilm-related processes. This is a fast, inexpensive and easy to use assay, and thus can be conducted for several compounds in different conditions. Results with one of our biofilm inhibitors indicate that this compound inhibits the expression of csgD, which encodes for the master regulator of Salmonella biofilms. This inhibition can be followed downstream the regulatory pathway of CsgD, as also directly regulated genes like adrA and csgB show a similar inhibition.
Since in situ biofilms can exist of more than one microbial species, it is essential for the future identification of new inhibitors to identify anti-biofilm targets which are of importance both in monospecies and multispecies biofilms. Therefore we compared by FACS analysis the expression of the promoter fusions in monospecies Salmonella biofilms and multispecies biofilms containing Salmonella. Some genes showed a high and similar expression in monospecies and multispecies biofilms (without being expressed in free-living cultures) and therefore form good targets for new anti-biofilm strategies. On the other hand we also found unique expression patterns of Salmonella in multispecies versus monospecies biofilms, indicating that the increased complexity and higher heterogeneity in multispecies biofilms influences gene expression of Salmonella.