Can Fungi Feast on Radiation to Survive—and Thrive?

Recent research into fungi and radiation

Radiation-absorbing Fungi growing around Chernobyl. Image provided by YourStory

Humans have been aware of the uses of Fungi since the first morsel of cheese was made, a loaf of soft, steamy bread was baked, and the first tub of grapes was turned into wine. Scientifically, Fungi were first discovered by Heinrich Anton de Bary in 1858 (Father of Mycology). Kingdom Fungi include eukaryotic, heterotrophic organisms that have long been used as a source of food and medicine (Penicillin) by humans.

A fungal diet ranges from plastics to asbestos, cardboard to fuels and even radiation!

Since the 1960s, it has been known that certain species of fungi are capable of withstanding high radiation levels as demonstrated by their growth on the high slopes of the Antarctica mountains (highest level of UV radiation). In the 1980s, a Ukrainian team discovered a black fungal growth in the pools of water and on the interior walls of Chernobyl’s destroyed Reactor 4. The fungi could not only withstand the radiation but it also rapidly grew towards the highest levels.

Years of research later Ekaterina Dadachova and her colleagues at the Albert Einstein College of Medicine in New York discovered that some fungi could use melanin, a pigment found in the human skin, to harvest the energy from radiation and use it for their growth. These fungi were later called radiotrophic fungi. Some examples of radiotrophic fungi are:

• Cryptococcus neoformans - one of the species found near Chernobyl - uses radiosynthesis to convert ionizing radiation into energy similar to photosynthesis (conversion of carbon dioxide and water into glucose and oxygen). Scientists believe this fungus could protect humans by insulating them against deadly rays. Since radiation exposure is a serious concern among astronauts (due to the lack of a magnetic field), scientists aim to grow C.neoformans on the International Space Station (results are yet to be shared). One of the cons of this species is that it readily attacks immunocompromised people and causes a condition called cryptococcosis.

Distinguishing features of Cryptococcus neoformans: a) belong to the phylum Basidiomycota, b) capsules are produced in response to environmental cues, c) produce melanin in the presence of diphenolic molecules and turn brown/black. Image provided by Nature Publishing Group, Nature Reviews, Microbiology, “Deciphering the Model Pathogenic Fungus Cryptococcus neoformans.”

• Cladosporium sphaerospermum - This is a radiotrophic dematiaceous fungus that is typically found in decaying leaves and branches of citrus trees. Like C.neoformans, it also uses melanin to convert radiation into energy. It is rarely pathogenic (with only five cases of Cladosporium-induced pulmonary infections reported to date) and more often causes mild infections or acts as an allergen. It has potential applications in space exploration and radioactive waste degradation.

Cladosporium sphaerospermum( belongs to phylum Ascomycota). Image provided by iGUiecologia

• Wangiella dermatitidis - Commonly called Exophiala dermatitidis is highly resistant to ionizing radiation (more than any other fungi). It is a melanized yeast that can be found in soil and plants. It is an opportunistic fungal pathogen that causes occupational diseases in agricultural and fungal workers.

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Colonies of Exophiala dermatitidis cultivated on solid media. Pictures taken by a) stereo microscope and b) optical microscope.  Image provided by ResearchGate, Natural Science, “A Review beyond the borders: Proteomics of microclonial black fungi and black yeasts"

The above three strains are collectively known as black fungi due to their melanin concentrations. Radiation accident sites (like Chernobyl Reactor 4) have fungi with higher concentrations of melanin than the boundary/exclusion areas. During the conversion of radiation to chemical energy (for growth and development; radiosynthesis), fungal melanin molecules change shape such that it is four times better at carrying out a common metabolic chemical reaction. Additionally, melanin also helps combat environmental stresses.

With the rise in the levels of radiation pollution, ‘black fungi’ prove to be a reliable and sustainable treatment method. They also have applications in space exploration, radiation shielding and plastic degradation. Black fungi models have gained prominence in both fundamental and applied research. Based on the function of melanin in ‘black fungi’, research is being conducted to mimic the radiation harnessing capacity in humans. Despite their pathogenic nature, the potential applications of radiotrophic fungi in future technologies and human survival are vast and promising.

If future research is focused on harnessing beneficial properties and mitigating risks, addressing global health and environmental challenges would become a cakewalk!