Department of Pediatrics, Chung-Ang University Hospital, Seoul, 06973, South Korea.
College of Medicine, Chung-Ang University, Seoul, 06911, South Korea.
Exp Mol Med. 2020 Aug;52(8):1288-1297. doi: 10.1038/s12276-020-0470-5. Epub 2020 Aug 3.
The microbiota of human breast milk (HBM) contribute to infant gut colonization; however, whether bacterial extracellular vesicles (EVs) are present in HBM or might contribute to this process remains unknown. In this study, we characterized the HBM microbiota of healthy Korean mothers and measured the key bacteria likely affecting infant gut colonization by analyzing both the microbiota and bacterial EVs. A total of 22 HBM samples were collected from lactating mothers. The DNA of bacteria and bacteria-derived EVs was extracted from each sample. In alpha-diversity analyses, bacterial samples showed higher richness and evenness than bacterial EV samples, and beta-diversity analyses showed significant differences between bacteria and bacterial EVs within identical individual samples. Firmicutes accounted for the largest proportion among the phyla, followed by Proteobacteria, Bacteroidetes, and Actinobacteria, in both bacteria and bacterial EV samples. At the genus level, Streptococcus (25.1%) and Staphylococcus (10.7%) were predominant in bacterial samples, whereas Bacteroides (9.1%), Acinetobacter (6.9%), and Lactobacillaceae(f) (5.5%) were prevalent in bacterial EV samples. Several genera, including Bifidobacterium, were significantly positively correlated between the two samples. This study revealed the diverse bacterial communities in the HBM of healthy lactating mothers, and found that gut-associated genera accounted for a high proportion in bacterial EV samples. Our findings suggest the existence of key bacteria with metabolic activity that are independent of the major bacterial populations that inhabit HBM, and the possibility that EVs derived from these bacteria are involved in the vertical transfer of gut microbiota.
人乳（HBM）中的微生物群有助于婴儿肠道定植；然而，HBM 中是否存在细菌细胞外囊泡（EV），或者它们是否可能有助于这一过程尚不清楚。在这项研究中，我们对健康韩国母亲的 HBM 微生物群进行了表征，并通过分析微生物群和细菌 EV 来测量可能影响婴儿肠道定植的关键细菌。从哺乳期母亲中总共收集了 22 个 HBM 样本。从每个样本中提取细菌和细菌衍生 EV 的 DNA。在 alpha 多样性分析中，细菌样本的丰富度和均匀度高于细菌 EV 样本，而 beta 多样性分析显示相同个体样本中细菌和细菌 EV 之间存在显著差异。厚壁菌门在门水平上占比最大，其次是变形菌门、拟杆菌门和放线菌门，在细菌和细菌 EV 样本中均如此。在属水平上，细菌样本中以链球菌（25.1%）和葡萄球菌（10.7%）为主，而细菌 EV 样本中以拟杆菌（9.1%）、不动杆菌（6.9%）和乳杆菌科（f）（5.5%）为主。双歧杆菌等几个属在两个样本中呈显著正相关。本研究揭示了健康哺乳期母亲 HBM 中多样化的细菌群落，并发现与肠道相关的属在细菌 EV 样本中占很高比例。我们的研究结果表明，存在具有代谢活性的关键细菌，它们独立于栖息在 HBM 中的主要细菌群，并且这些细菌衍生的 EV 可能参与了肠道微生物群的垂直转移。
