B. thetaiotaomicron degraded lactose and HMOSs in the co-culture. (A) A generic representation of HMOS structure [46] and prediction of bacterial glycosyl hydrolase (GH) required to cleave the specific linkage. (B) Genome prediction for HMOS-degrading carbohydrate-active enzymes (CAZymes) for B. thetaiotaomicron and A. caccae. (C) The proposed mechanism for HMOS sequestration by B. thetaiotaomicron using polysaccharide utilization loci (PUL). Abbreviation: HMOS, human milk oligosaccharide; OM, outer membrane; PP, periplasm; CM, cytoplasmic membrane; Tr, transporter; SusC, SusC-like TonB-dependent transporter; SusD, SusD-like outer membrane-binding protein.