The Fecal Microbial Community of Breast-fed Infants from Armenia and Georgia

Oligosaccharides from breast milk are believed to help shape the infant intestinal microbiota through their ability to feed specific bacterial groups, in particular Bifidobacterium. In a subset of mothers the fucosyltransferase 2 (“secretor”) gene is mutationally inactivated, which leads to milk lacking 2’ fucosylated glycans and was previously shown to impact microbial colonization of the neonate gut. Similarly, infants may receive distinct individual bacterial exposures which influence their gut communities over time. Here we study the infant gut microbiota through a longitudinal study on cohorts of breast-fed infants from the neighboring countries of Armenia and Georgia. Marker gene sequencing of 16S ribosomal genes revealed that the gut microbial communities of infants from these countries were dominated by bifidobacteria, were different from each other, and were marginally influenced by their mother’s secretor status. Species-level differences in the bifidobacterial communities of each country and birth method were also observed. These community differences suggest that environmental variation between individuals in different locations may influence the gut microbiota of infants, possibly through selection or seeding differences.

母乳低聚糖被认为可通过滋养特定细菌类群（尤其是双歧杆菌（Bifidobacterium）），助力塑造婴儿肠道微生物组。在部分母亲亚群中，岩藻糖基转移酶2（fucosyltransferase 2，又称"分泌型（secretor）"）基因发生突变失活，导致其乳汁中缺乏2’-岩藻糖基化聚糖（2’ fucosylated glycans）；既往研究已证实，该状态会影响新生儿肠道的微生物定植。类似地，婴儿可能会接触到各异的特异性细菌，这些细菌会随时间推移对其肠道菌群结构产生影响。本研究针对亚美尼亚与格鲁吉亚这两个邻国的母乳喂养婴儿队列开展纵向研究，以此探究婴儿肠道微生物组的特征与影响因素。通过对16S核糖体基因（16S ribosomal genes）的标记基因测序分析，研究发现两国婴儿的肠道微生物群均以双歧杆菌为优势类群，但两国菌群结构存在显著差异，且仅受母亲分泌型状态的微弱影响。研究还观测到不同国家间双歧杆菌群落的物种水平差异，以及与分娩方式相关的群落差异。上述群落结构差异表明，不同地域个体间的环境异质性可能通过菌群筛选或定植接种的差异，影响婴儿的肠道微生物组。