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A type of bacteria called Deinococcus radiodurans, nicknamed “Conan the Bacterium” for its ability to survive the harshest of extremes, can withstand radiation doses 28,000 times greater than those that would kill a human being — and the secret to its success is rooted in an antioxidant.
Now, scientists have uncovered how the antioxidant works, unlocking the possibility that it could be used to protect the health of humans, both on Earth and those exploring beyond it in the future.
The antioxidant is formed by a simple group of small molecules called metabolites, including manganese, phosphate and a small peptide, or molecule, of amino acids.
Together, this powerful trilogy is more effective in protecting against radiation than manganese combined with just one of the other components, according to a new study published Monday in the Proceedings of the National Academy of Sciences.
The findings could be used to protect astronauts from high doses of cosmic radiation on future deep-space missions across our solar system, according to the study authors.
“We’ve long known that manganese ions and phosphate together make a strong antioxidant, but discovering and understanding the ‘magic’ potency provided by the addition of the third component is a breakthrough. This study has provided the key to understanding why this combination is such a powerful — and promising — radioprotectant,” said study coauthor Brian Hoffman, the Charles E. and Emma H. Morrison Professor of Chemistry and professor of molecular biosciences at Northwestern University’s Weinberg College of Arts and Sciences, in a statement.
Uncovering an antioxidant’s secret
Previous research has shown that Deinococcus, known as the most radiant-resistant life-form in the Guinness World Records, can survive outside of the International Space Station for three years. The hardy bacteria can also withstand acid, cold and dehydration.
Hoffman and Michaely Daly, Uniformed Services University of the Health Sciences professor of pathology, also demonstrated the bacteria’s incredible survivability. The October 2022 report, which the duo coauthored with a team of researchers, showed that if Deinococcus ever existed on Mars, the frozen microbes could have survived for millions of years.
For the previous study, the team measured the amount of manganese antioxidants in the cells of the bacteria. The researchers found that the amount of radiation that a microorganism could survive was directly related to its amount of manganese antioxidants. So the more manganese antioxidants present, the more resistance to radiation.
When dried and frozen, Deinococcus radiodurans could survive 140,000 grays, or units of X-and gamma-ray radiation, which is 28,000 times greater than the amount of radiation that could kill a person.
For the latest research, Hoffman, Daly and their colleagues used MDP, or melatonin-derived protective, a synthetic antioxidant inspired by Deinococcus radiodurans that Daly designed. This antioxidant has been used in radiation-inactivated polyvalent vaccines, which rely on radiation to shut down pathogens like chlamydia. Daly, who has studied Deinococcus radiodurans for years, is also on the National Academies’ Committee on Planetary Protection.
The study team analyzed how MDP’s active components, including manganese, phosphate and a peptide called DP1, protect cells and proteins from radiation exposure. When the peptide and phosphate bind to manganese, they create a ternary, or triple, complex that is highly effective in protecting against radiation. Together, the metabolites in MDP create a “secret sauce,” Hoffman said.
Dr. Tetyana Milojevic, chair of exobiology at the University of Orléans in France, said the study provides new insights into how radioprotective shields could be created by metabolites, and potentially enhanced in the future. Tetyana was not involved in the study.
“This new understanding of MDP could lead to the development of even more potent manganese-based antioxidants for applications in health care, industry, defense and space exploration,” Daly said.
Daly noted that astronauts on deep-space missions would be exposed to high levels of radiation, primarily from energetic particles traveling through the cosmos called cosmic rays.
“MDP, being a simple, cost-effective, nontoxic, and highly effective radioprotector, could be administered orally to mitigate these space radiation risks,” he said.
On Earth, the antioxidant could be used for protection against accidents that release radiation.
Now, the team is curious to see whether this triple complex behind Deinococcus’ antioxidant exists in cells of other organisms, and if so, if they could be responsible for radiation-resistance in them, Hoffman said.
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