Birth, Development, Disease

“The birth canal is very heavily colonized by bacteria,” said Maria Dominguez-Bello, a University of Puerto Rico biologist who has been studying microbiota around the world, including among isolated tribes in the Amazon. “We think that is not by chance.”

The rising number of C-section babies denied this colonization, along with the casual use of antibiotics and other factors that can alter the microbiota, might help explain trends such as rising incidents of asthma and food allergies caused by misfiring immune systems. To explore this, researchers have begun following C-section babies, comparing their microbiomes and their health with babies delivered through the birth canal.

The interaction between the microbiota and the immune system may also play a role in other diseases in adults, including those caused at least in part by chronic inflammation from hyperactive immune systems.

“Gut bacteria have figured out a way to network with our immune system so it doesn’t attack them,” said Sarkis K. Mazmanian of the California Institute of Technology.

The microbiota apparently sends signals that dampen the “inflammatory response,” a crucial defense also thought to play a role in a variety of diseases, including many forms of cancer, the “metabolic syndrome” caused by obesity, diabetes and heart disease.

The theory is that one reason some people may be prone to these diseases is that they are missing certain microbes. One anti-inflammatory compound produced by a bacterium appears to cure the equivalent of colitis and multiple sclerosis in mice, both of which are caused by misfiring immune systems, Mazmanian found.

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