Head : Alexandra Gruss

• Scientifics objectives :
  

Identification of factors favoring adaptation, establishment and spread of opportunistic pathogens and lactic acid bacteria in dairy products and in vivo.

Milk is a rich medium that allow growth of i) lactic acid bacteria (LAB), which are used to promote fermentation in food processing, and ii) opportunistic pathogens, which are contaminants. Both kinds of bacteria are well adapted for growth in this medium, where they can reach high concentrations.

Food-mediated transmission of pathogens could be a key step in their dissemination and establishment in animals as well as in humans. Indeed, once the food is ingested, bacteria are in contact with the gut mucosa, and can eventually colonize or infect the host.

We are studying bacterial species belonging to the group of Gram-positive bacteria with a low GC content, including Lactococcus lactis (used in food fermentations), Enterococcus faecalis, Staphylococcus aureus and Streptococcus agalactiae (present as commensal bacteria and opportunistic pathogens).

Our goals are to characterize factors that favor establishment of food bacteria or opportunistic pathogens within a dairy food product, and once ingested, within the host. We would like to know whether some of these factors favor the establishment in both environments.
Such factors could be strain-specific, e.g. linked to a pathogenicity island, or on the contrary, shared by a set of phylogenetically related bacteria. We use different strategies to identify both kinds of factors involved in the establishment of bacteria in a given biotope.

Our laboratory has expertise in bacteriology (using genetics, genomics, and biochemistry), dairy technology and bio-informatics. This allows us to build multidisciplinary projects:

• Predictions starting from comparative genomic databases are tested experimentally, 
  
• Bench results are put to the test in "real" dairy technology conditions in our P2 confinement level dairy.

• Our research themes are the following :

•  Establishment: Factors mediating immobilization of bacteria.

• Competition: Role of peptide transport in nutrition and signaling; modes of stabilizing surface proteins.

• Survival: Metabolic adjustments made by bacteria when confronted with oxygen.

• Adaptation: Differential expression of bacterial genes and regulatory RNAs in dairy products or in animals as compared to in vitro laboratory cultures.

• Evolution: Bioinformatic analyses of the conserved genomic backbone versus the strain-specific sequences among food-fermenting and oppotunistic bacteria.. (see : http://genome.jouy.inra.fr/mosaic)

• Ecosystems: Dynamics of bacterial populations in complexe ecosystems such as fermented dairy food products, studied in situ in a cheese factory with P2 level of confinement.

• Départment

The UBLO lab is part of the INRA Department of Microbiology and Food Safety