Human milk contains a high concentration of complex oligosaccharides that influence the composition of the intestinal microbiota in breast-fed infants. Previous studies have indicated that select species such as Bifidobacterium longum subsp. infantis and Bifidobacterium bifidum can utilize human milk oligosaccharides (HMO) in vitro as the sole carbon source, while the relatively few B. longum subsp. longum and Bifidobacterium breve isolates tested appear less adapted to these substrates. Considering the high frequency at which B. breve is isolated from breast-fed infant feces, we postulated that some B. breve strains can more vigorously consume HMO and thus are enriched in the breast-fed infant gastrointestinal tract. To examine this, a number of B. breve isolates from breast-fed infant feces were characterized for the presence of different glycosyl hydrolases that participate in HMO utilization, as well as by their ability to grow on HMO or specific HMO species such as lacto-N-tetraose (LNT) and fucosyllactose. All B. breve strains showed high levels of growth on LNT and lacto-N-neotetraose (LNnT), and, in general, growth on total HMO was moderate for most of the strains, with several strain differences. Growth and consumption of fucosylated HMO were strain dependent, mostly in isolates possessing a glycosyl hydrolase family 29 α-fucosidase. Glycoprofiling of the spent supernatant after HMO fermentation by select strains revealed that all B. breve strains can utilize sialylated HMO to a certain extent, especially sialyl-lacto-N-tetraose. Interestingly, this specific oligosaccharide was depleted before neutral LNT by strain SC95. In aggregate, this work indicates that the HMO consumption phenotype in B. breve is variable; however, some strains display specific adaptations to these substrates, enabling more vigorous consumption of fucosylated and sialylated HMO. These results provide a rationale for the predominance of this species in breast-fed infant feces and contribute to a more accurate picture of the ecology of the developing infant intestinal microbiota.
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机译：人乳包含高浓度的复杂寡糖，这些寡糖会影响母乳喂养婴儿肠道菌群的组成。先前的研究表明，选择的物种如长双歧杆菌亚种。 infantis 和双歧双歧杆菌可以在体外利用人乳低聚糖（HMO）作为唯一碳源，而长双歧杆菌相对较少。长短双歧杆菌和短双歧杆菌的分离物似乎不太适合这些底物。考虑到短双歧杆菌从母乳喂养的婴儿粪便中分离的频率很高，我们推测一些短双歧杆菌菌株可以更强烈地消耗HMO，因此在母乳喂养的婴儿胃肠道中富集。为了对此进行检验，对许多来自母乳喂养婴儿粪便的短双歧杆菌分离株进行了表征，证明它们存在参与HMO利用的不同糖基水解酶，以及它们在HMO或特定HMO物种（如乳酸菌）上的生长能力。 N -四糖（LNT）和岩藻糖半乳糖。所有短双歧杆菌菌株在LNT和乳酸- N -新四糖（LNnT）上均表现出高水平的生长，并且一般而言，大多数菌株在总HMO上的生长是中等的，并且存在几个菌株差异。岩藻糖基化的HMO的生长和消耗是菌株依赖性的，主要是在具有糖基水解酶家族29α-岩藻糖苷酶的分离株中。某些菌株对HMO发酵后的废上清液进行糖谱分析表明，所有短杆菌都可以在一定程度上利用唾液酸化的HMO，特别是唾液酸-乳糖- N -四糖。有趣的是，在中性LNT之前，菌株SC95耗尽了这种特定的寡糖。总的来说，这项工作表明短双歧杆菌中的HMO消耗表型是可变的。但是，某些菌株对这些底物表现出特定的适应性，从而可以更强力地消耗岩藻糖基化和唾液酸化的HMO。这些结果为该种在母乳喂养的婴儿粪便中占主导地位提供了理论依据，并有助于更准确地了解正在发育的婴儿肠道菌群的生态状况。
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