Fungi could eat dangerous radiation to survive, an unexpected finding that could one day help feed astronauts in space — at least those willing to eat a crawling fungus.
The research began with the discovery of black fungus growing on the walls of the damaged, highly radioactive Chernobyl nuclear reactor and collected by robots.
The fungus was rich with melanin, the same pigment that gives human skin its color, protecting the skin from solar and ultraviolet radiation. Melanin is found in many, if not most, fungal species.
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"The fungal kingdom comprises more species than any other plant or animal kingdom," said researcher Arturo Casadevall, an immunologist at Albert Einstein College of Medicine in New York.
Nuclear and other high-energy reactions give off ionizing radiation — dangerous rays and particles that can damage genes and thus cause mutations, and eventually cancer.
"Just as the pigment chlorophyll converts sunlight into chemical energy that allows green plants to live and grow," so might melanin help fungi make use of ionizing radiation, said nuclear medicine specialist Ekaterina Dadachova at the Albert Einstein College of Medicine.
The scientists experimented on three species of fungi. They consistently found that ionizing radiation significantly boosted the growth of fungi that contained melanin.
"In general we think of radiation as something bad or harmful. Here we have a situation where these fungi appear to benefit, which is unexpected," Casadevall told LiveScience.
For example, the researchers exposed two kinds of fungi — one that naturally contained melanin (Wangiella dermatitidis) and another that scientists induced to make the pigment (Crytococcus neoformans) — to levels of ionizing radiation about 500 times higher than normal, the doses one might see at high altitudes where atmospheric shielding from cosmic rays is lessened.
Both species grew significantly faster, as detailed in the May 23 issue of the journal PLoS ONE.
The researchers stressed these findings do not mean fungi can eat radioactive matter and somehow cleanse it. Rather, the fungi can simply harness the energy that radioactive materials give off.
The ability of fungi to live off ionizing radiation could prove useful to people.
"Since ionizing radiation is prevalent in outer space, astronauts might be able to rely on fungi as an inexhaustible food source on long missions or for colonizing other planets," Dadachova said.
Casadevall also noted that the melanin in fungi is no different chemically from the melanin in human skin.
"It's pure speculation — but not outside the realm of possibility — that melanin could be providing energy to skin cells," he said. "While it wouldn't be enough energy to fuel a run on the beach, maybe it could help you to open an eyelid."
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