Story at a Glance.
We used to call it gut flora but now it’s referred to by the very scientific name of microbiota. We’ve been researching the role of microbiota and its connection with our immune system since the late 1990’s. If the staggering numbers of our gut microbiota kind of make you glaze over, you’re not alone; tens of trillions is the latest count. There are at least 1,000 different types of bacteria with more than 3 million genes. In total they can weight up to two kilograms. That’s a lot of gut flora in anyone’s language.
Interestingly we have about a third of our gut microbiota in common with other people. But two thirds is specific to us individually. Now that may not seem very important, but it is. Microbiota plays a major role in the homeostasis of our body, that is, the regulation of the normal functioning of our body. In fact it is so important that scientists have started to refer to the collective of microbiota (microbiome) as the ‘forgotten organ’.
It may have a role in autoimmune diseases, diabetes, rheumatoid arthritis, muscular dystrophy, multiple sclerosis, fibromyalgia and even some cancers. Microbiomes have been linked to modifying the regulation of neurotransmitters in the body, which has far reaching implications in depression, anxiety and other emotional states. The possibilities of this ecological community of microorganisms is staggering.
Up until now, this ‘forgotten organ’ was viewed as an ‘acquired organ’, because you don’t get it until after you were born. They believed that babies were born sterile, that their intestinal colonisation only started after birth and continued as they grew. That is, until now…
The scientists at The University of Bern in Switzerland have been studying what goes on in the maternal gut and how it shapes the immune system of her offspring. Whilst it was known that a newborn’s gut influenced its own immune system, the impact of the mother’s microbiota on her baby had been largely unexplored, until this point.
Mercedes Gomez de Agüero et al. conducted a study1 on mice to observe if the maternal microbiome affected their offspring’s immune system during gestation. In order to achieve this they contaminated microbe-free pregnant mice with E.coli that was designed to dissipate over time. That is, by the time the mice gave birth they were no longer infected with the E.coli.
“By transiently colonizing pregnant female mice, we show that the maternal microbiota shapes the immune system of the offspring,” the study noted.
What transpired was that offspring born to the infected mothers had increased numbers of innate lymphoid and mononuclear cells in their intestines and different patterns of gene expression in their guts. Gene expressions that included those that influence cell division and differentiation, mucus and ion channels, and metabolism and immune function. It rapidly becomes clear that the maternal microbiota shapes the immune system of her offspring.
The study concluded, “Pups born to mothers transiently colonized in pregnancy are better able to avoid inflammatory responses to microbial molecules and penetration of intestinal microbes.”
It appears that the more we learn about the gut and the microbiota, the more we comprehend its intrinsic significance. This advance in the understanding of the very complex and diverse world of microbiomes is yet another step forward in our appreciation of the importance of the health of our gut.
 The Maternal Microbiota Drives Early Postnatal Innate Immune Development. Mercedes Gomez De Agüero, Stephanie C. Ganal-Vonarburg, Tobias Fuhrer, Sandra Rupp, Yasuhiro Uchimura, Hai Li, Anna Steinert, Mathias Heikenwalder, Siegfried Hapfelmeier, Uwe Sauer, Kathy D. Mccoy, Andrew J. Macpherson. Science, 2016 DOI: 10.1126/science.aad2571