Table 1.

List of genes whose product is directly involved in bifidobacteria-host interaction.

	Genes	Gene product	Product function
Sortase-dependent pili	fimA/P	Major pilin subunit	Structural element of sortase-dependent pili.
	fimB/Q	Minor or ancillary pilin subunit
	strA	Sortase (transpeptidase enzyme)	Sortase-dependent pilus assembly and anchoring to the cell surface.
Tight Adherence pili	tadA	ATPase
	tadB	Integral membrane protein	Formation of hetero- and homo-polymers involved in the secretion apparatus of the pilus subunits.
	tadC	integral membrane protein
	tadE	Pseudopilin	Structural pilus components synthetized as prepilins.
	tadF	Pseudopilin
	Flp	Prepilin
	tadV	Peptidase (enzyme)	Post-translational processing of prepilins to remove their hydrophobic leader peptide to obtain structural pilus components.
Quorum sensing	luxS	S-ribosylhomocysteine lyase	It catalyzes the transformation of S-ribosylhomocysteine to homocysteine and 4,5-dihydroxy-2,3-pentadione, the latter known as the precursor of the autoinducer-2 (AI-2).
sEPS	Conserved gene set involved in sEPS production	Priming glycosyl transferase	It catalyzes the addition of the first saccharidic moiety to a lipophilic carrier molecule for initiation of sEPS repeating unit assembly.
		Glycosyl transferases	They are involved in the assembly of sEPS repeating units.
		Flippases and/or ABC transporters	Enzymes involved in the transport of sEPS subunits from the cytoplasm to the outer membrane environment.
		Subunit polymerase	It catalyzes the polymerization of sEPS subunits.
		Chain length determinant proteins	They determine the polymer chain length.
		Carbohydrate precursor biosynthesis/modification enzymes	They catalyze the biosynthesis of sEPS precursor and the conversion of the latter into sEPS subunits.