The human microbiome is a highly complex community of microorganisms that conveniently does good for our health while we provide it with a cozy place to live. With the advent of sequencing technology, scientists have taken the opportunity to explore this ecosystem in detail to find the story behind these microbes. They have been asking who’s there, where are they located, and what exactly are they doing? Although we’ve made quite some progress in answering these questions, one that has received relatively less attention is, when do we acquire our microbiome?
The current dogma is that the human fetus is sterile and that colonization with microbes begins during exit from the birth canal. The vaginal microbiota is therefore a primary source of microbes for the infant gut microbiota and contribute to the newborn’s health (babies born by C-section are at higher risk of developing allergic disease (1)).
In previous posts we’ve looked at breast milk as an additional source of microbes and also questioned whether the human fetus is indeed sterile. In a recent review published in PLoS Biology (2), Lisa Funkhouser and Seth Bordenstein discuss these internal and external modes of microbial transmission in greater detail. In an added bonus to summarizing the current literature for humans/mice, they consider an evolutionary perspective of symbiotism and feature examples of microbial transmission in marine invertebrates, terrestrial invertebrates, and vertebrates. It’s an insightful look at the mechanisms that different species uses to make sure offspring get their dose of essential microbes.
The review reads like an episode of Planet Earth and is sure to be both entertaining and educational.