CU Boulder researchers discover dirt molecule can ease stress

The molecule brings them one step to closer to a "stress vaccine"

Christopher Lowry, associate professor of integrated physiology, is senior author on a study on how .
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Everyone remembers someone who would eat dirt on the playground at recess. Turns out, those kids might have known something the others didn’t.

University of Colorado Boulder researchers have discovered that a specific strain of bacteria found in soil can help protect people against stress.

Christopher Lowry, an integrative physiology professor and senior author on the study published Monday, said researchers are looking at using the bacteria to treat mental health issues such as post-traumatic stress disorder.

To do so, they isolated a single molecule of the bacteria that appears to block receptors that get inflamed during stressful times.

“One of the burning questions is, essentially, what are the critical components of the bacteria that seem to benefit the host?” Lowry said.

The critical component is a fatty acid called 10(Z)-hexadecenoic acid that is found in Mycobacterium vaccae. Lowry said researchers conducted a screen where they exposed human cells to the bacteria, looking for the extracts that suppressed inflammation in the cells.

As far as the researchers can tell, he said, the only bacteria that produce this lipid are microbacteria, many of which come from soil and water.

Lowry said he hopes to use the bacteria to create a “stress vaccine” for those with high-stress jobs, such as first responders and soldiers.

Researchers have seen positive results in animal models so far, which have responded to injections of the bacteria with less stress-induced inflammation.

“We think this may be a novel strategy for prevention and treatment of psychiatric issues,” Lowry said.

He expects the vaccine could be ready in 10 to 15 years. The same strain of bacteria has been studied in clinical trials for other conditions, such as tuberculosis, and has a good safety record, making it easier to advance as a treatment.

The idea that a molecule from soil bacteria could help those suffering with stress follows both the hygiene hypothesis and the idea that inflammation can cause mental health issues like depression or anxiety.

The hygiene hypothesis was first proposed by a British scientist, David Strachan, in 1989, according to a news release from the university. He suggested the “modern, sterile world” was leading to impaired immune systems. Researches have since said it is really a lack of exposure to “old friends,” like microbes in the environment.

“As people have moved toward more urban living, we have less exposure to these types of microorganism that you find in the soil and consequently our immune systems are hyper responsive,” Lowry said.

He has published several studies on this issue, including one that found children raised in pet-free urban households are more likely to have a higher inflammatory response to stressors than those raised on farms.

Being exposed to nature can be good in a variety of ways, and some even advocate giving out “green prescriptions,” Lowry said. While he thinks there are probably several factors at play, bacteria might be one of them.

“We used to think that microbacteria weren’t an important part of the human microbiome,” Lowry said. But, a 2015 study found a “hidden microbacterium” in healthy people’s mouths, teeth and upper airways, he said.

The bacteria likely came from dust and municipal water supplies.

Lowry suggests people try to diversify and maximize their exposures. That can mean spending time outdoors in different ecosystems and eating a variety of plant food. Each plant has its own microbiome, with up to 100,000 bacteria that live inside of it.

Man’s best friend, the dog, also can help, he said. Studies have shown exposure to a dog in the first two years of life can protect people against allergies later.

“The power of nature continues to amaze and surprise us as scientists and we look forward to learning more,” he said.

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