Einstein researchers' discover 'radiation-eating' fungi

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Public release date: 22-May-2007

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Albert Einstein College of Medicine

http://www.eurekalert.org/pub_releases/2007-05/aeco-erd051607.php

Einstein researchers' discover 'radiation-eating' fungi

Finding could trigger recalculation of Earth's energy balance and

help feed astronauts

Scientists have long assumed that fungi exist mainly to decompose

matter into chemicals that other organisms can then use. But

researchers at the Albert Einstein College of Medicine of Yeshiva

University have found evidence that fungi possess a previously

undiscovered talent with profound implications: the ability to use

radioactivity as an energy source for making food and spurring their

growth.

" The fungal kingdom comprises more species than any other plant or

animal kingdom, so finding that they're making food in addition to

breaking it down means that Earth's energetics—in particular, the

amount of radiation energy being converted to biological energy—may

need to be recalculated, " says Dr. Arturo Casadevall, chair of

microbiology & immunology at Einstein and senior author of the

study, published May 23 in PLoS ONE.

The ability of fungi to live off radiation could also 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, " says Dr.

Ekaterina Dadachova, associate professor of nuclear medicine and

microbiology & immunology at Einstein and lead author of the study.

Those fungi able to " eat " radiation must possess melanin, the

pigment found in many if not most fungal species. But up until now,

melanin's biological role in fungi—if any--has been a mystery.

" Just as the pigment chlorophyll converts sunlight into chemical

energy that allows green plants to live and grow, our research

suggests that melanin can use a different portion of the

electromagnetic spectrum—ionizing radiation—to benefit the fungi

containing it, " says Dr. Dadachova.

The research began five years ago when Dr. Casadevall read on the

Web that a robot sent into the still-highly-radioactive damaged

reactor at Chernobyl had returned with samples of black, melanin-

rich fungi that were growing on the reactor's walls. " I found that

very interesting and began discussing with colleagues whether these

fungi might be using the radiation emissions as an energy source, "

says Dr. Casadevall.

To test this idea, the Einstein researchers performed a variety of

in vivo tests using three genetically diverse fungi and four

measures of cell growth. The studies consistently showed that

ionizing radiation significantly enhances the growth of fungi that

contain melanin.

For example, two types of fungi--one that was induced to make

melanin (Crytococcus neoformans) and another that naturally contains

it (Wangiella dermatitidis)—were exposed to levels of ionizing

radiation approximately 500 times higher than background levels.

Both species grew significantly faster (as measured by the number of

colony forming units and dry weight) than when exposed to standard

background radiation.

The researchers also carried out physico-chemical studies into

melanin's ability to capture radiation. By measuring the electron

spin resonance signal after melanin was exposed to ionizing

radiation, they showed that radiation interacts with melanin to

alter its electron structure. This is an essential step for

capturing radiation and converting it into a different form of

energy to make food.

Dr. Casadevall notes that the melanin in fungi is no different

chemically from the melanin in our skin. " It's pure speculation but

not outside the realm of possibility that melanin could be providing

energy to skin cells, " he says. " 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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Other Einstein researchers involved in the study are Ruth A. ,

Xianchun Huang, Moadel, D. Schweitzer, Philip Aisen

and D. Nosanchuk.

PLEASE NOTE: Upon its publication, the article will be freely

available online at the PLoS ONE website:

http://www.plosone.org/doi/pone.0000457.