Einstein researchers' discover 'radiation-eating' fungi
- Finding could trigger recalculation of Earth's energy balance and help
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
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.
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
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."