-Caveat Lector-
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From: [EMAIL PROTECTED]
Date: August 21, 2007 1:27:36 AM PDT
To: [EMAIL PROTECTED]
Cc: [EMAIL PROTECTED], [EMAIL PROTECTED], [EMAIL PROTECTED]
Subject: (3) Expanding the Limits of What Conditions Living
Creatures Can Endure
Soaking Up Radiation
Summary (Jun 01, 2007): Researchers have found that fungi may be
able to use radioactivity as an energy source for making food and
spurring growth. The findings may have profound implications for
how we understand the cycles of biologically available energy for
life, and could also have important applications for space
exploration.
Based on a Albert Einstein College of Medicine news release
http://www.astrobio.net/news/modules.php?
op=modload&name=News&file=article&sid=2349&mode=thread&order=0&thold=0
Wangiella dermatitidis is one type of fungi exposed to ionizing
radiation in the study.
Credit: University of Adelaide
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 new findings could alter the way we think about
how energy is made available to life on Earth, and could have
profound implications for our understanding of how life has adapted
and evolved over time on our planet.
"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.
An example of melanized fungal cells observed by the research team.
Credit: Dadachova/Albert Einstein College of Medicine of Yeshiva
University/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."
------------------
The Limits of Organic Life
Summary (Jul 10, 2007): A new report from the National Research
Council discusses why the search for life in the solar system may
need to include looking for life that doesn't have the same
biochemistry as life on Earth.
Based on a National Academies news release
http://www.astrobio.net/news/modules.php?
op=modload&name=News&file=article&sid=2390&mode=thread&order=0&thold=0
The search for life elsewhere in the solar system and beyond should
include efforts to detect what scientists sometimes refer to as
"weird" life -- that is, life with an alternative biochemistry to
that of life on Earth -- says a new report from the National
Research Council.
The committee that wrote the report found that the fundamental
requirements for life as we generally know it -- a liquid water
biosolvent, carbon-based metabolism, molecular system capable of
evolution, and the ability to exchange energy with the environment
-- are not the only ways to support phenomena recognized as life.
"Our investigation made clear that life is possible in forms
different than those on Earth," said committee chair John Baross,
professor of oceanography at the University of Washington, Seattle.
The report emphasizes that "no discovery that we can make in our
exploration of the solar system would have greater impact on our
view of our position in the cosmos, or be more inspiring, than the
discovery of an alien life form, even a primitive one. At the same
time, it is clear that nothing would be more tragic in the American
exploration of space than to encounter alien life without
recognizing it."
The tacit assumption that alien life would utilize the same
biochemical architecture as life on Earth does means that
scientists have artificially limited the scope of their thinking as
to where extraterrestrial life might be found, the report says. The
assumption that life requires water, for example, has limited
thinking about likely habitats on Mars to those places where liquid
water is thought to be present or have once flowed, such as the
deep subsurface.
Extreme environments, like the exceedingly dry Atacama Desert in
Chile, harbor unique organisms that can survive in some of the
harshest conditions on Earth.
Credit: Aaron Gronstal
However, according to the committee, liquids such as ammonia or
formamide could also work as biosolvents -- liquids that dissolve
substances within an organism -- albeit through a different
biochemistry. The recent evidence that liquid water-ammonia
mixtures may exist in the interior of Saturn's moon Titan suggests
that increased priority be given to a follow-on mission to probe
Titan, a locale the committee considers the solar system's most
likely home for weird life.
"It is critical to know what to look for in the search for life in
the solar system," said Baross. "The search so far has focused on
Earth-like life because that's all we know, but life that may have
originated elsewhere could be unrecognizable compared with life
here. Advances throughout the last decade in biology and
biochemistry show that the basic requirements for life might not be
as concrete as we thought."
Besides the possibility of alternative biosolvents, studies show
that variations on some of the other basic tenets for life also
might be able to support weird life. DNA on Earth works through the
pairing of four chemical compounds called nucleotides, but
experiments in synthetic biology have created structures with six
or more nucleotides that can also encode genetic information and,
potentially, support Darwinian evolution.
Additionally, studies in chemistry show that an organism could
utilize energy from alternative sources, such as through a reaction
of sodium hydroxide and hydrochloric acid, meaning that such an
organism could have an entirely non-carbon-based metabolism.
Researchers need to further explore variations of the requirements
for life with particular emphasis on origin-of-life studies, which
will help determine if life can exist without water or in
environments where water is only present under extreme conditions,
the report says. Most planets and moons in this solar system fall
into one of these categories. Research should also focus on how
organisms break down key elements, as even non-carbon-based life
would need elements for energy, structure, and chemical reactions.
The report also stresses that the future search for alien life
should not exclude additional research into terrestrial life.
Through examination of extreme environments, such as deserts and
deep under the oceans, studies have determined that life exists
essentially anywhere water and a source of energy are found
together on Earth. Field researchers should therefore seek out
organisms with novel biochemistries and those that exist in areas
where vital resources are scarce to better understand how life on
Earth truly operates, the committee said. This improved
understanding will contribute greatly toward seeking Earth-like
life where the conditions necessary for its existence might be met,
as in the case of subsurface Mars.
Space missions will need adjustment to increase the breadth of
their search for life. Planned Mars missions, for example, should
include instruments that detect components of light elements --
especially carbon, hydrogen, oxygen, phosphorous, and sulfur -- as
well as simple organic functional groups and organic carbon. Recent
evidence indicates that another moon of Saturn, Enceladus, has
active water geysers, raising the prospect that habitable
environments may exist there and greatly increasing the priority of
additional studies of this body.
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