Modulation of the eps-ome transcription of bifidobacteria through simulation of human intestinal environment

Bacteria are able to synthesize a variety of polysaccharides with different functions that can be classified according to their sugar composition (homo- or hetero-polysaccharides) and their location on the cell surface. In this context, capsular polysaccharides are bound to the cell surface, while exopolysaccharides or EPS are secreted and released in the environment. In gut commensals, these macromolecules are claimed to protect bacterial cells against gastrointestinal challenges and to be involved in modulating the cross talk with the host. Bifidobacteria are indigenous inhabitants of the human gastro intestinal tract and are one of the first bacterial colonizers following birth. The predicted EPS arsenal of the Bifidobacterium genus, which we designate here as the eps-ome, consists of nine eps gene clusters conserved among different bifidobacterial species and a further 44 unique eps loci, together representing a large proportion of the inter(sub)species variability identified among bifidobacterial genomes. Moreover, phenotypic analyses highlighted not a consensus phenotype of EPS production. Co-cultivations of bifidobacterial species in media simulating adult and infant human gut environments was shown to prompt an enhancement of the number of genes transcribed in all strains tested in monoassociation and multi-associations. Transcription of eps genes was enhanced in fecal media, compared to reference condition in both mono- or multi- associations experiments. In particular, transcriptomic analyses resulted in an increased transcription of key genes for EPS biosynthesis, including glycosyltransferaseencoding genes, as well as genes specifying EPS transporter and polysaccharide biosynthesis protein.