Bacteroides thetaiotaomicron Fosters the Growth of Butyrate-Producing Anaerostipes caccae in the Presence of Lactose and Total Human Milk Carbohydrates

Abstract

The development of infant gut microbiota is strongly influenced by nutrition. Human milk oligosaccharides (HMOSs) in breast milk selectively promote the growth of glycan-degrading microbes, which lays the basis of the microbial network. In this study, we investigated the trophic interaction between <i>Bacteroides thetaiotaomicron</i> and the butyrate-producing <i>Anaerostipes caccae</i> in the presence of early-life carbohydrates. Anaerobic bioreactors were set up to study the monocultures of <i>B. thetaiotaomicron</i> and the co-cultures of <i>B. thetaiotaomicron</i> with <i>A. caccae</i> in minimal media supplemented with lactose or a total human milk carbohydrate fraction. Bacterial growth (qPCR), metabolites (HPLC), and HMOS utilization (LC-ESI-MS²) were monitored. <i>B. thetaiotaomicron</i> displayed potent glycan catabolic capability with differential preference in degrading specific low molecular weight HMOSs, including the neutral trioses (2'-FL and 3-FL), neutral tetraoses (DFL, LNT, LNnT), neutral pentaoses (LNFP I, II, III, V), and acidic trioses (3'-SL and 6'-SL). In contrast, <i>A. caccae</i> was not able to utilize lactose and HMOSs. However, the signature metabolite of <i>A. caccae</i>, butyrate, was detected in co-culture with <i>B. thetaiotaomicron</i>. As such, <i>A. caccae</i> cross-fed on <i>B. thetaiotaomicron</i>-derived monosaccharides, acetate, and d-lactate for growth and concomitant butyrate production. This study provides a proof of concept that <i>B. thetaiotaomicron</i> could drive the butyrogenic metabolic network in the infant gut.