454 pyroqsequencing of 16S v4 amplicons from dichorionic triplet fecal samples.

Monozygotic and dizygotic twin studies investigating the relative roles of host genetics and environmental factors in shaping gut microbiota composition have produced conflicting results. In this study, we investigated the gut microbiota composition in a healthy dichorionic triplet set. Dichorionic triplet sets contain a pair of monozygotic twins and a naturally occurring control, the fraternal triplet, with similar pre- and post-natal environmental conditions. V4 16S rRNA pyrosequencing was employed to investigate microbiota composition, and the species and strain diversity of the culturable bifidobacterial population was also examined. At month 1, the gut microbiota of all infants was dominated by bifidobacteria, with the monozygotic pair sharing a similar microbiota compared to their fraternal sibling. This colonisation pattern was similar at months 2 and 3; however by month 12, there was no greater similarity observed in the microbiota profile of the monozygotic pair compared to the fraternal sibling. Principal Coordinate Analyses (PCoA) plots of the microbiota composition at month 12 appeared equally dissimilar amongst all three. The microbiota of two antibiotic-treated dichorionic triplet sets was also investigated. Not surprisingly, in both cases early life antibiotic administration appeared to be the major overriding determinant of microbiota composition at month 1, irrespective of zygosity. By month 12, early antibiotic administration appeared to no longer influence the gut microbiota composition. We hypothesize that initially host genetics play a significant role in the composition of an individual’s gut microbiota unless an antibiotic intervention is given, but by month 12 environmental factors are the major determinant.