Beyond applying sunscreen before a day at the beach, we generally don’t think much about our exposure to radiation. We have Earth’s magnetic field to thank for that, but for astronauts who go beyond the planet’s protective layer, sunscreen won’t quite cut it.

A fungus found growing in the aftermath of Chernobyl, however, might.

Cladosporium spaerospermum is one such radiation-loving fungal species, found on Earth in extreme places, like the remains of the Chernobyl Nuclear Power Plant in Ukraine. While most plants use energy from the sun for photosynthesis, this type of fungus draws its energy from radiation in a process called radiosynthesis.

Researchers believe large amounts of melanin in the cell walls of these fungi protect the cells from radiation damage, with melanin now being explored as biotechnological means of radiation shielding.

For applications in space, researchers offer different approaches:

Ekaterina Dadachova, professor of pharmacy at the University of Saskatchewan, Canada, wants astronauts to eat more mushrooms; Nils Averesch, research engineer at Stanford, would rather grow a thick layer of fungus on spacecraft and future Martian or lunar habitats. Averesch isn’t joking — to bring radiation exposure down to Earth-like levels, a habitat on Mars would need an estimated “2.3m layer of melanized fungal biomass.”

Remember: These radiotrophic fungi are already in space. A survey of the environmental contamination on board the International Space Station (ISS) revealed many fungal species on surfaces and in the air, including Aspergillus, Penicillium and Saccharomyces species. Although the ISS still enjoys some shielding from the Earth’s magnetosphere, it receives elevated levels of radiation compared with Earth, and astronauts can stay in orbit for up to only a year.

“Life emerged on Earth at a time when there was much higher background radiation, and early life forms must have considerable radiation resistance,” Dadachova says in her article for Current Opinion in Microbiology. “Although current background radiation levels are much lower than in the early days on Earth, earthly life still exists in a field of radiation.”

Dadachova highlights the “Evolution Canyon” site in Israel, where the two slopes of the canyon, separated by just 200 meters of open grassland, represent drastically different biomes. The south-facing slope receives 200-800 percent more solar radiation than the north-facing slope, which is temperate and shady.

The south-facing slope is populated by many species of melanized fungi, such as Aspergillus niger, which contains “three times more melanin than the same species from the north-facing slope.”

Melanin pigments are found in all biological kingdoms, suggesting these compounds are ancient molecules that emerged early in the course of evolution.

Dadachova’s research examines the radioprotective effects of melanized fungi in patients undergoing radiation therapy for cancer treatment and believes there could be potential for protecting people in prolonged space flight.

CAPTION: Cladosporium spaerosporium IMAGE: Shutterstock

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Speaking about mice fed black mushrooms being protected from high doses of external radiation, Dadachova says: “It’s not like you can eat a mushroom and be protected forever, but if you experience a radiation influx while the mushroom’s melanin is in your digestive tract, it protects it from really high doses of radiation.”

“Very recently, we obtained soluble fungal melanin which can be given after exposure to radiation to mitigate radiation damage,” Dadachova tells KUST Review.

Dadachova’s team fed soluble allomelanin to mice that had been exposed to high doses of gamma radiation. They found the effects of the radiation were mitigated when allomelanin was administered within 24 hours of irradiation.

“Based on these findings, soluble allomelanin derived from a fungal source could serve as an easily sourced, cost-effective and viable countermeasure to accidental radiation exposure,” Dadachova says. “This is an important step forward in this melanin and radiation investigation.”

Stanford’s Averesch was part of the research team investigating just how well Cladosporium spaerospermum can grow in space. Petri dishes loaded with the fungus were sent to the ISS and oriented so they faced away from Earth. To compare, a number of petri dishes with the same fungus remained earthside.

The team found the fungi onboard the ISS had a microbial growth advantage, which could be associated with increased radiation in space. The melanized fungal biomass may have radioprotective properties and could even be used as an energy-storage device on spacecraft.

“Solutions to radiation exposure on interplanetary travel are more restricted by up-mass limitations than any other factor of space travel,” Averesch says. “Being living organisms, micro-fungi self-replicate from microscopic amounts, which could allow significant weight savings. Biotechnology would thus prove to be an invaluable asset to life support and resource management for explorers on future missions to the moon, Mars and beyond.”