Friday, December 17, 2010

Fungi found growing in remains of the Chernobyl reactor.

Fungi have been found growing in the remains of the Chernobyl Atomic Energy Station and surrounding areas. Their secret: use the radiation to grow!

After nearly two weeks without writing anything of substance due to overbearing exams, I'm finally back in action! To jump directly back into science, we'll be discussing a very weird property of certain fungi that have been found living in the Chernobyl nuclear reactor. They've not only figured out how to live with radiation levels many times that of the normal background, but they've also found a way to use it as an energy source for growth!

Radiation is dangerous, that's something no one needs to be reminded of. But scientists studying the wreckage of the Chernobyl nuclear power station in the Ukraine have found fungi living in the depths of the reactor where radiation levels are extremely high ( up to 500 times the regular background radiation).

What's the secret to their success? The fungi contain lots of melanin, the pigment that's responsible for darkening skin colour, has been shown to be an extremely useful radio protector, a substance that can protect against radiation damage. This isn't really anything new as melanin has been shown to block out harmful UV radiation from the sun; however, radiation from the Chernobyl reactor wreckage is much more damaging than its lower energy counterpart, UV. So how does melanin block out such high energy radiation?

Radiation damages our cells primarily by causing the production of free radicals, highly unstable chemical compounds that tend to react with our DNA. Melanin (and many pigments for that matter) contain their own radicals that stabilize the radicals produced by high energy radiation, thereby reducing the damage to our genes.

It's quite miraculous that many of these fungi are able to live in such hostile environments, ones in which humans start showing symptoms of radiation sickness within minutes. The more interesting thing though was that these fungi were able to use the radiation as a form of energy, thereby increasing their rate of growth.

The studies conducted on many of the species have found that they feed off of radioactive graphite ( a radioactive form of Carbon-14) from the reactor core; they essentially use nuclear waste as a food source. One species in particular even grew under extremely nutrient poor conditions.The radiation itself was shown to increase the electron-transfer properties of melanin, particularly the speed of the reaction, which resulted in higher metabolic rates for the fungus. Higher metabolic rates means faster growth for the fungi containing large levels of melanin.

Many species also exhibited some form of chemotaxis towards radioactive sources. Fungal hyphae were found to grow towards sources of ionizing radiation. They really do think of it as a source of food!

There are several implications of this discovery, the most important for our own future seems to be the use of these species to dispose of nuclear waste. Removal of fuel waste by these sources could end up making nuclear power a more attractive alternative energy source in the near future, thereby eliminating dependence on fossil fuels which contribute substantially to global warming.

An even more bizarre suggestion was to use these fungi as food for astronauts on long interplanetary flights. The rationale being that solar UV radiation could be used to power a nearly endless food supply on board spacecraft. If we ever do adopt this form of food distribution for the general population, let me gladly be the first to say "pass the radioactive mushrooms".


(Full paper available here)
Dadachova E, Bryan RA, Huang X, et al. (2007). Ionizing Radiation Changes the Electronic Properties of Melanin and Enhances the Growth of Melanized Fungi. PLoS One; 2(5): e457.

Zhdanova NN, Tugay T, Dighton J, et al. (2004). Ionizing radiation attracts soil fungi. Mycol Res; 108(9): 1089-96.


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