Of microbes and mothers '“ certain gut bacteria in mice can disrupt the mother-child relationship

(The Conversation is an independent and nonprofit source of news, analysis and commentary from academic experts.) Bill Sullivan, Indiana University (THE CONVERSATION) There is perhaps nothing more heartbreaking and confusing than a mother who neglects her children. In 2017, approximately 675,000 children in the U.S. were victims of mistreatment, with 75% reported as neglected. The early postnatal months are critical to ensure proper physical and psychological development; children who are neglected during this phase can experience stunted growth as well as behavioral and learning problems. What could possibly subvert the basic instinct for a mother to take care of her child? Scientists have uncovered a number of biological and environmental factors that can influence maternal behavior in numerous types of mammals. Many of these studies have pointed to deficits in oxytocin, a hormone released during birth and while breastfeeding that facilitates mother-child bonding. Defects in the levels of serotonin, a key neurotransmitter that regulates mood and depression, can also interfere with the maternal instinct. Recently a research team from the Salk Institute in La Jolla, California, led by Janelle Ayres reported a new influence on maternal behavior arising from an unexpected source: the bacteria that dwell in the mother’s gut. Their intriguing study, published in Science Advances, was performed using mouse mothers and their offspring. As a pharmacologist and microbiologist at the Indiana University School of Medicine, and author of ‘œPleased to Meet Me: Genes, Germs, and the Curious Forces That Make Us Who We Are,’� I study the surprising effects that microbiota ‘” the microbes that live on and inside another organism ‘” have on behavior. Ayres’ study has uncovered a new way that microbiota can fundamentally alter behavior in mice, including a basic instinct such as motherly nurturing. Proper development of newborns depends on microbiota Emerging research is uncovering a clear role for intestinal microbiota in the proper development of newborns, including humans. Our intestines are populated by trillions of bacteria, which are first introduced into the body by the mother during birth. Mice are frequently used by scientists to gain insights into potential functions the microbiota may have in humans. By feeding them high doses of antibiotics, researchers can create ‘œgerm-free’� mice that lack microbiota. Alternatively, germ-free mice can be birthed using sterile techniques. Germ-free mice grow more slowly and suffer from a number of immune system deficits and social behavior issues. In addition to helping digest food and manufacture nutrients, a newborn’s gut bacteria regulate production of insulin-like growth factor 1, a crucial growth hormone and that promotes proper development of bone and tissues. In Ayres’ new study, she and her colleagues found a novel way that intestinal microbes contribute to mother-child bonding. For the first time, her research team found that the mother’s microbiota can impact her behavior in a way that can be detrimental to her pups. While it is widely accepted that an infant’s microbiota is important for proper development, the affect of the mother’s microbiota on nurturing behavior had not been previously considered. Ayres’ team administered several different kinds of E. coli bacteria into germ-free mice and discovered that mothers housing one called E. coli O16:H48 had pups with stunted growth. Pups born to these mothers had impaired signaling through the insulin-like growth factor 1 that led to less fat and muscle development. How microbes cause a mother to neglect her offspring