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

Abstract

Multiple factors help shape the infant intestinal microbiota early in life. Environmental conditions such as the presence of bioactive molecules from breast milk dictate gut microbial growth and survival. Infants also receive distinct, personalized, bacterial exposures leading to differential colonization. Microbial exposures and gut environmental conditions differ between infants in different locations, as does the typical microbial community structure in an infant's gut. Here we evaluate potential influences on the infant gut microbiota through a longitudinal study on cohorts of breast-fed infants from the neighboring countries of Armenia and Georgia, an area of the world for which the infant microbiome has not been previously investigated. 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.

Figure 1. Infant gut microbiome clusters using a Bray-Curtis distance metric and a Non-metric multidimensional scaling (NMDS) ordination.

CST = community state type.

Figure 2. Members of the infant gut microbiome with greater than 0.05% average relative abundance over time based on proportion of sequencing reads.

Error bars are standard error. (A) Average proportion of major gut microbes by country. (B) Average proportion of major gut microbes by birth method. (C) Average proportion of major gut microbes by mother’s secretor status. H = heterozygote, S = homozygote secretor, N = non-secretor, U = unknown.

Figure 3. Average relative abundance of each member within the genus Bifidobacterium over time, based on the Bif-TRFLP/BLIR data.

Error bars are standard error. (A) Average proportion of bifidobacteria by country. (B) Average proportion of bifidobacteria by birth method. (C) Average proportion of bifidobacteria by mother’s secretor status. H = heterozygote, S = homozygote secretor, N = non-secretor, U = unknown.

Figure 4. Bifidobacterial relative abundance over time by secretor genotype.

The lines show the average bifidobacterial abundance of each group over time. H = heterozygote, S = homozygote secretor, N = non-secretor, U = unknown.