DAIRY BACTERIAL ECOSYSTEMS Team leaders : Agnès Delacroix-Buchet

RESEARCH PROJECTS

• Identify factors that favor growth of food bacteria or the appearance of food pathogens in a model biotope, by following the dynamics of bacterial populations in controlled dairy ecosystems such as milk, fermented milk, and cheese. Observations made ‘in vitro' by the URLGA research teams are tested in such ecosystems. These include identification of factors mediating :

1.  attachment, establishment and formation of biofilms,
2.  proteolysis and maturation of surface proteins,
3. peptide transport,
4. possible positive effects of selected strains on the ecosystem equilibrium,
5. long term survival and metabolic adaptation,
6. in situ expression of virulence factors and toxin production.

• Determine the extent to which milk quality (i.e., origin and composition in relation to animal genotype, and technological treatments) affects quality of the final dairy product, as well as growth of dairy bacteria ;

• Develop small scale cheese models (500 mL to 20 L) in a confined environment (pilot P2 cheese production plant) ;

• Develop and apply tools for rapid analysis of dairy bacterial ecosystems (genetic and taxonomic tools for bacteria).

• Develop and validate ‘safe' models for microbial risk assessment, to be used under real industrial conditions. Identify factors involved in bacterial dissemination in dairy products.

• Distinguish factors involved in virulence and those involved in multiplication and survival in foods. Validate observations realized by research groups working on lactic acid bacteria or food pathogens under laboratory conditions, by reproducing them in natural ecosystems such as those employed for cheese production.

• Answer consumer expectations for food sanitary security, and health effect of dairy products, by an improved knowledge of the parameters and the dynamics of dairy ecosystems.

• In the long run, perform epidemiological studies on the maintenance of specific virulence factors during bacterial propagation in foods (screening for genes coupled with identification of virulence factors implicated or not in growth).

FINANCING