Mom knows best: the universality of maternal microbial transmission

Abstract

The sterile womb paradigm is an enduring premise in biology that human infants are born sterile. Recent studies suggest that infants incorporate an initial microbiome before birth and receive copious supplementation of maternal microbes through birth and breastfeeding. Moreover, evidence for microbial maternal transmission is increasingly widespread across animals. This collective knowledge compels a paradigm shift—one in which maternal transmission of microbes advances from a taxonomically specialized phenomenon to a universal one in animals. It also engenders fresh views on the assembly of the microbiome, its role in animal evolution, and applications to human health and disease.

Figure 1. Sources of microbial transmission in humans from mother to child.

Cut-away diagram highlighting the various internal and external sources of maternal microbial transmission as well as the species that are commonly associated with transfer from those regions. Regions discussed include the oral cavity ,, the mammary glands ,,, the sebaceous skin surrounding the breast ,, the vaginal tract ,,, and the intrauterine environment ,,,,,–,. Illustration by Robert M. Brucker.

Figure 2. Examples of animals that exhibit microbial maternal transmission.

(A) Pea aphid (Acyrthosiphon pisum), photo credit: Whitney Cranshaw, Colorado State University/©Bugwood.org/CC-BY-3.0-US; (B) Domesticated chicken hen (Gallus gallus domesticus), photo credit: Ben Scicluna; (C) Sockeye salmon (Oncorhynchus nerka), photo credit: Cacophony; (D) South American river turtle (Podocnemis expansa), photo credit: Wilfredor. All photos were obtained from Wikimedia Commons (www.commons.wikimedia.org).