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

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.

母乳来源的低聚糖（Oligosaccharides）被认为可通过滋养特定细菌类群，尤其是双歧杆菌属（Bifidobacterium），助力塑造婴儿肠道微生物群。部分母亲体内的岩藻糖基转移酶2（fucosyltransferase 2，即"分泌型"）基因发生突变失活，导致其乳汁缺乏2’-岩藻糖基化聚糖，且此前已有研究证实该情况会影响新生儿肠道的微生物定植。同样地，不同婴儿的细菌接触暴露情况存在差异，这些差异会随时间推移塑造其肠道微生物群落。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，以此解析婴儿肠道微生物群的特征。通过对16S核糖体基因（16S ribosomal genes）的标记基因测序分析，本研究发现：两国婴儿的肠道微生物群落均以双歧杆菌为优势类群，但两国群落结构存在显著差异，且受母亲分泌型状态的影响程度有限。此外，本研究还观察到两国婴儿的双歧杆菌群落以及不同分娩方式下的双歧杆菌群落均存在物种水平的差异。上述群落差异表明，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群。