Nature is filled with examples of extreme life (aka. extremophiles), which are so-called because they can withstand extreme conditions. These include organisms that can survive in extremely dry conditions, extreme temperatures, acidity, pressure, and even the vacuum of space. The study of these organisms not only helps scientists learn more about the kinds of environments life can survive (and even thrive) in. It also helps astrobiologists to speculate about possible life in the Universe. Perhaps the name “tardigrades” (aka. “water bears”) rings a bell, those little creatures that could survive in interstellar space?
Then you have Deinococcus radiodurans (D. radiodurans), which microbiologists call “Conan the Bacterium” due to its ability to tolerate the harshest conditions. This includes radiation doses thousands of times higher than what would kill a human, or any other organism on Earth, for that matter. In a new study, a team of researchers from Northwestern University and the Uniformed Services University (USU) characterized a synthetic organism inspired by Deinococcus radiodurans that could allow humans to withstand the elevated radiation levels in deep space, on the Moon, and Mars.
The research was led by Hao Yang, a Research Assistant Professor at Northwestern University’s Department of Chemistry. He was joined by Ajay Sharma, also a Research Assistant Professor of Chemistry at Northwestern; Michael J. Daly, a Professor of Pathology at the Uniformed Services University (USU); and Brian M. Hoffman, the Charles E. and Emma H. Morrison Professor of Chemistry and molecular biosciences at Northwestern. The paper detailing their findings appeared on November 8th in the Proceedings of the National Academy of Sciences (PNAS).
Hoffman is the Charles E. and Emma H. Morrison Professor of Chemistry and professor of molecular biosciences and a member of the Chemistry of Life Processes Institute and the Robert H. Lurie Comprehensive Cancer Center at Northwestern University. Daly, an expert on Deinococcus radiodurans, is also a member of the National Academies’ Committee on Planetary Protection. In a previous study, Hoffman and Daly investigated D. radiodurans‘ ability to withstand radiation on Mars. Earlier research has shown that the bacterium can survive 25,000 grays, which is five times the lethal dose for a human.
However, Hoffman and Daly found that D. radiodurans could withstand 140,000 grays when dried or frozen – 28,000 times the lethal dose for a human! This means that frozen microbes beneath the surface of Mars could survive the cosmic and solar radiation the planet is exposed to on a daily basis. The key to its resistance, they determined, is simple metabolites that combine with manganese to form a powerful antioxidant. They also found that the radiation dose a microorganism can survive is directly related to the amount of manganese antioxidants it contains.
In this latest study, the research team describes a synthetic designer antioxidant (MDP) inspired by D. radiodurans that is much more effective at resisting radiation. Building on their previous efforts, Hoffman and Daly’s team investigated a designer decapeptide (DP1) that, when combined with phosphate and manganese, forms the free-radical-scavenging agent MDP, which is even better at protecting against radiation damage than D. radiodurans. As Hoffman explained in a Northwestern Now news release:
“It is this ternary complex that is MDP’s superb shield against the effects of radiation. 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.”
“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,” said Daly. Potential applications include synthetic antioxidants that could help protect astronauts from radiation during long-duration missions to deep space. In another study, Daly and his collaborators found MDP is effective in preparing irradiated polyvalent vaccines. This could also have applications for space medicine, ensuring that vaccines typically rendered inactive by radiation remain effective.
Further Reading: Northwestern Now, PNAS