Let's talk about radiotrophic fungi.
I want to start with the most surprising fact about them: they don't just SURVIVE in high radiation environments, they grow at *FOUR TIMES* the rate they would in background radiation.
Our best guess is they're "eating" radiation.
The key is melanin, similar to the melanin that darkens your skin & protects you from UV damage. It's a dark, high molecular weight pigment polymer, absorbing 99.9% of UV & visible light.
Ionizing radiation beyond UV can change the electronic/chemical structure of melanin, making it act similar to chlorophyll in its ability to capture photons and generate electron gradients.
SOURCE: ncbi.nlm.nih.gov/pmc/articles/P…
Given these electron gradients and a carbon source, the fungi can synthesize basic nutrients, or metabolize environmental nutrients at a greater rate.
In 1986, dark, melanin-producing (melanotic) fungi were found on the walls of the Chernobyl reactor & in the cooling tower water. Samples of these fungi, when exposed to a radiation source, were observed to grow TOWARDS the source, along a gradient of increasing gamma exposure.
Other melanotic fungi have been found growing freely on Mir and ISS space stations, where radiation limits human habitation length.
They're also found in the mountains of Antarctica, suggesting the melanin is providing protection from cold or desiccation or simply the unshielded UV exposure of the South Polar region.
Space colonization might well benefit from a radiation shield that can be grown on other worlds from regolith and ionizing radiation, or protect travelers in transit.
A 3 in (9 cm) layer of Martian regolith colonized by these fungi would effectively absorb most or all of the damaging radiation at the Martian surface.
All of this is hypothetical, of course, but certainly piques my curiosity.
Some interesting sources to start your own exploration:
"Ionizing Radiation: how fungi cope, adapt, and exploit with the help of melanin"
Curr Opin Microbiol. 2008 Dec; 11(6): 525–531.
ncbi.nlm.nih.gov/pmc/articles/P…
"Chernobyl mold could shield astronauts from deep-space radiation"
engadget.com/international-…
"Fungi and ionizing radiation from radionuclides"
FEMS Microbiol Lett. 2008 Apr;281(2):109-20.
academic.oup.com/femsle/article…
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