Factors Influencing Microbiota Diversity and Composition During Early Postnatal Development

Abstract

The human gut and brain have a bidirectional communication that has shown to play a pivotal role in our health and disease. Literature has shown that microbiota composition and diversity can be influenced by both genetic and environmental factors, contributing to shaping an individual’s microbial composition. The current work includes analysis of the microbiome of several mouse models to better understand how gene-environmental interactions during early development can influence the composition of microbiota within the gut. Here, male and female mice from several strains (C57BL/6, Balb/C, FVB, CD1) and genetically modified mice including T-cell receptor knock out mice (TCRβ-/-δ-/-) and Fragile-X-mice (FMR1-KO) were exposed to early life stressors including lipopolysaccharide (LPS) injection on postnatal day 3 (P3) and/or overnight maternal separation on P9. Fecal samples were collected at P24 and microbiota composition was determined by amplifying the 16s rRNA gene variable 3(v3) region and sequenced using the MiSeq Illumina platform. DADA2, was used to analyze this data in R software. Among the group, strain was found to be significant among alpha and beta diversity metrics while sex and stress were found to contribute to within strain variation, which demonstrated that both genetic and environmental factors are important in shaping an individual’s microbial composition. Secondly, we also explored the role of gut microbiota on the development of the immune system in TCRβ-/-δ-/- and C57BL/6 mice. Mice that lack T-lymphocytes were found to have a lower alpha diversity, as well as separated from their wild-type controls by beta diversity. Several bacterial taxa were found to be influenced by the immune system, demonstrating a bidirectional communication between the gut and T-cells. Lastly, the influence of litter, an environmental factor on microbial composition was explored within inbred mouse strains, C57BL/6 and Balb/C. Litter was found to influence alpha diversity, in which litters among C57BL/6 exhibited the greatest variation in such diversity. Beta diversity was also found to be influenced by litter, as related litters were found to cluster together. Differences in bacterial taxa between the inbred strains were observed and a subset of those taxa were found to be influenced by litter. Hierarchical clustering and co-occurrence analysis revealed different clusters of co-occurring taxa between both strains. These findings demonstrate that environmental factors can contribute to influence the composition of microbiota.