Microbiota control of maternal behavior regulates early postnatal growth of offspring

Maternal-offspring bonding and maturation of maternal behavior is necessary during the early postnatal period of an infant to promote optimal development and growth. The regulation of maternal behavior is multifactorial relying both on sensory cues including auditory and olfactory signals emitted by the infant and received by the mother, as well as proper neuroendocrine responses including that of the oxytocin system. The intestinal microbiota has emerged as a critical regulator of growth and development in the early postnatal period of an individual’s life. While, this is best appreciated in the context of direct interactions between the microbiota and the infant, the microbiota can indirectly influence postnatal growth and development by regulating maternal factors. Here, we describe the identification of an intestinal E. coli strain that is pathogenic to the maternal-offspring system during the early postnatal stage of life and results in growth stunting of the offspring. However, rather than having a direct pathogenic effect on the infant, we found that this particular E. coli strain was pathogenic to the dams by interfering with the maturation of maternal behavior. The poor maternal behavior resulted in malnourishment of the pups and impaired IGF-1 signaling leading to the consequential stunted growth. Our work provides a new understanding of how the microbiota regulates postnatal growth and an additional variable that must be considered when studying the regulation of maternal behavior.