symbiosis

See the following -

The Way You’re Born Can Mess With The Microbes You Need To Survive

Martin J. Blaser | Wired | April 3, 2014

Throughout the animal kingdom, mothers transfer microbes to their young while giving birth. [...] [For] millennia, mammalian babies have acquired founding populations of microbes by passing through their mothers’ vagina. This microbial handoff is also a critical aspect of infant health in humans. Today it is in peril. Read More »