Bifidobacterium species diversity in breast milk samples (lanes 1 to 22) as determined by DGGE. Dominant bands were identified as corresponding to B. adolescentis (a), B. adolescentis (b), B. bifidum (c), B. longum (d), B. adolescentis (e), B. adolescentis (f), Bifidobacterium spp. (97% B. adolescentis) (g), B. longum (h), B. breve (i), B. dentium (j), and B. breve (k). M1 to M4 are markers.