Newly identified nutrient helps the gut remember past infections and kill invading bacteria

Scientists studying the body’s natural defenses against bacterial infections have identified a nutrient – taurine – that helps the gut remember past infections and kill invading bacteria, such as Klebsiella pneumoniae (Kpn). The discovery, published in the journal Cell by scientists from five National Institutes of Health institutes, could contribute to efforts to find alternatives to antibiotics.

Scientists know that the microbiota – the trillions of beneficial microbes living harmoniously in our gut – can protect people from bacterial infections, but little is known about how they provide protection. Scientists study the microbiota with the goal of finding or improving natural treatments to replace antibiotics, which harm the microbiota and become less effective as bacteria develop resistance to drugs.

Scientists observed that microbiota that had already been infected and transferred to germ-free mice helped prevent infection with Kpn. They identified a class of bacteria –Deltaproteobacteria– involved in the fight against these infections, and further analysis led them to identify taurine as the trigger of Deltaproteobacteria activity.

Taurine helps the body digest fats and oils and is naturally found in bile acids in the intestine. Toxic hydrogen sulfide gas is a by-product of taurine. Scientists believe that low levels of taurine allow pathogens to colonize the gut, but high levels produce enough hydrogen sulfide to prevent colonization. During the study, the researchers realized that a single mild infection was enough to prepare the microbiota to resist further infection, and that the liver and gallbladder – which synthesize and store bile acids containing taurine – may develop protection against long-term infections.

The study found that taurine given to mice as a supplement in drinking water also prepared the microbiota to prevent infection. However, when the mice drank water containing bismuth subsalicylate – an over-the-counter medicine commonly used to treat diarrhea and upset stomach – the protection against infection decreased because bismuth inhibits production of hydrogen sulfide.

Scientists from the National Institute of Allergy and Infectious Diseases at the NIH led the project in collaboration with researchers from the National Institute of General Medical Sciences; the National Cancer Institute; the National Institute of Diabetes and Digestive and Kidney Diseases; and the National Institute for Research on the Human Genome.