Host- Microbe interaction: the case of bifidobacteria as key example of gut commensals

Bifidobacteria are one of the most dominant members of the human intestinal microbiota of infants and their presence has been associated with health promoting effects. So these microorganisms are commonly used as health-promoting or probiotic ingredient of various functional foods. Although the accepted importance of bifidobacteria in the gut, only recent genomics-based studies (probiogenomics) have significantly enhanced our knowledge on the physiology, genetics and evolutionary development of these probiotic bacteria Probiogenomics analyses applied to bifidobacteria has helped us to understand the mechanisms by which these bacteria adapt to the specific environment of the gastrointestinal tract, while also revealing genetic functions that mediate specific host-microbe interactions. The aim of this PhD thesis research is to shed light into the genetic and functional characteristics of bifidobacteria present in the human gut using genome sequencing and post-genomics based approaches. This study offers first evidences about the contribution of extracellular structures such as pili encoded by bifidobacteria in sustaining a specific mechanism of interaction with the human host.