Mold is generally something one would not want to find inside one’s body. However, in the case of Mucor racemosus, there may be compelling reasons to make an exception. This is because, according to a new study published in the journal PNAS, this symbiotic fungus—which inhabits the human gut—is capable of protecting us from radiation.
It might seem a bit far-fetched, but this is not the first time we have seen fungi doing strange things involving radiation.
We know that various radiation-resistant fungi exist, including species that survive X-ray doses 200 times higher than the lethal dose for humans.
There is also the fascinating world of radiotrophic fungi that use radiation as an energy source—such as the peculiar fungus that thrives amidst the radioactive debris of the Chernobyl nuclear power plant.
M. racemosus has a different trick up its sleeve regarding radiation, but it is no less impressive.
In their research, a team of scientists from China discovered that this fungus can provide radiation protection to its host through several different mechanisms, suggesting that the presence of M. racemosus in the gut could be beneficial.
In experiments involving irradiated mice, researchers found that animals treated with M. racemosus experienced less weight loss, inflammation, and oxidative stress compared to control mice that did not receive the fungus; this suggests that M. racemosus exerted a radioprotective effect on the treated animals. This radioprotective effect was enhanced when researchers pre-adapted the fungus to the low-oxygen conditions of the gut.
When germ-free mice (raised without microorganisms) were administered the fungus, they also showed reduced markers of radiation damage compared to control animals, suggesting that M. racemosus helps protect against the harmful effects of radiation independently of the host’s microbiota.
“These results demonstrate that M. racemosus directly mitigates radiation-induced intestinal damage in mice,” the researchers explain.
Regarding the mechanism by which M. racemosus achieves this, subsequent studies on irradiated intestinal cells and mice identified three amino acids produced by the fungus that may explain its radioprotective properties: L-glutamic acid, L-aspartic acid, and DL-lysine.
According to the researchers, these three amino acids directly contribute to DNA repair and intestinal tissue regeneration following radiation exposure.
However, this is not the only way the fungus performs its function.
Another chemical produced by the fungus, called methylthioadenosine (MTA), also plays a key role in radioprotection, even though it does not directly heal radiation-induced damage in the same way as the three amino acids.
Instead, it appears that the production of MTA by M. racemosus modulates the growth of the bacterium Limosilactobacillus reuteri and reprograms it to increase the production of a chemical called methionine; higher levels of methionine appear to enhance protection against radiation. In a final experiment evaluating the therapeutic potential of M. racemosus, researchers fed irradiated mice cheese fermented with the fungus and found that it reduced intestinal inflammation, improved intestinal barrier integrity, and lowered systemic inflammatory markers compared to mice fed cheese without the fungus.
While much more research is needed before concluding that everyone should consume M. racemosus as part of a balanced diet, the researchers note that the fungus already occurs in nature or is added to certain fermented foods and is FDA-approved for food use.
However, since M. racemosus can pose a health risk to immunocompromised individuals, we should exercise caution as we determine how best to integrate this fungus into the food pyramid or your home medicine cabinet—and perhaps among its fungal counterparts as well.
“More broadly, these results demonstrate that filamentous fungi are underappreciated yet influential players in the microbiota-host axis,” the researchers write, “and could be harnessed to mitigate the effects of radiation exposure and other diseases.”
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