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Organized Oral Session

Hybrid Session

Session: : When Does History Matter During Community Assembly?

OOS 53-2 - Priority effects and human milk oligosaccharides shape the structure of infant gut associated Bifidobacterium communities

Thursday, August 10, 2023
8:15 AM – 8:30 AM PDT
Location: 255
The postpartum microbial colonization period is critical for gut microbiota development, and bifidobacteria are among the first colonizers of the infant gut. Early colonization by bifidobacteria is facilitated by their ability to metabolize human milk oligosaccharides (HMOs) found in breastmilk. However, little is known about the mechanisms of community assembly of bifidobacterial communities. By applying assembly theory to a community of four representative infant-type Bifidobacterium species that employ varied strategies for HMO consumption, we show that arrival order and sugar utilization phenotypes significantly affected community formation. Bifidobacterium bifidum and Bifidobacterium longum subsp. infantis, two avid HMO consumers, dominate through inhibitory priority effects. Bifidobacterium breve, a species with limited HMO-utilization ability, can benefit from facilitative priority effects and dominates by utilizing fucose, an HMO degradant left unconsumed by the other bifidobacterial species. Analysis of publicly available breastfed infant fecal metagenome data showed that the observed trends for B. breve were consistent with our in vitro data, suggesting that priority effects may have contributed to its dominance. Our study highlights the importance and history dependency of initial community assembly and its implications for the maturation trajectory of the infant gut microbiota.