Posts Tagged ‘arsenic based life’

Tenacious life: Microbe swaps phosphorous for arsenic

December 2, 2010
Lakeside of the Mono Lake with Tufa columns in...

Mono Lake: Image via Wikipedia

The New York Times has the story that has been buzzing all day:

Scientists said Thursday that they had trained a bacterium to eat and grow on a diet of arsenic, in place of phosphorus — one of six elements considered essential for life — opening up the possibility that organisms could exist elsewhere in the universe or even here on Earth using biochemical powers we have not yet dared to dream about.

The bacterium, scraped from the bottom of Mono Lake in California and grown for months in a lab mixture containing arsenic, gradually swapped out atoms of phosphorus in its little body for atoms of arsenic.

Scientists said the results, if confirmed, would expand the notion of what life could be and where it could be. “There is basic mystery, when you look at life,” said Dimitar Sasselov, an astronomer at the Harvard-Smithsonian Center for Astrophysics and director of an institute on the origins of life there, who was not involved in the work. “Nature only uses a restrictive set of molecules and chemical reactions out of many thousands available. This is our first glimmer that maybe there are other options.”

Felisa Wolfe-Simon, a NASA astrobiology fellow at the United States Geological Survey in Menlo Park, Calif., who led the experiment, said, “This is a microbe that has solved the problem of how to live in a different way.”

This story is not about Mono Lake or arsenic, she said, but about “cracking open the door and finding that what we think are fixed constants of life are not.”

Dr. Wolfe-Simon and her colleagues publish their findings Friday in Science.

Gerald Joyce, a chemist and molecular biologist at the Scripps Research Institute in La Jolla, Calif., said the work “shows in principle that you could have a different form of life,” but noted that even these bacteria are affixed to the same tree of life as the rest of us, like the extremophiles that exist in ocean vents.

“It’s a really nice story about adaptability of our life form,” he said. “It gives food for thought about what might be possible in another world.

Phosphorus is one of six chemical elements that have long been thought to be essential for all Life As We Know It. The others are carbon, oxygen, nitrogen, hydrogen and sulfur.

While nature has been able to engineer substitutes for some of the other elements that exist in trace amounts for specialized purposes — like iron to carry oxygen — until now there has been no substitute for the basic six elements. Now, scientists say, these results will stimulate a lot of work on what other chemical replacements might be possible. The most fabled, much loved by science fiction authors but not ever established, is the substitution of silicon for carbon.

Phosphorus chains form the backbone of DNA and its chemical bonds, particularly in a molecule known as adenosine triphosphate, the principal means by which biological creatures store energy. “It’s like a little battery that carries chemical energy within cells,” said Dr. Scharf. So important are these “batteries,” Dr. Scharf said, that the temperature at which they dissolve, about 160 Celsius (320 Fahrenheit), is considered the high-temperature limit for life.

Arsenic sits right beneath phosphorus in the periodic table of the elements and shares many of its chemical properties. Indeed, that chemical closeness is what makes it toxic, Dr. Wolfe-Simon said, allowing it to slip easily into a cell’s machinery where it then gums things up, like bad oil in a car engine.

A bacterium known as strain GFAJ-1 of the Halomonadaceae family of Gammaproteobacteria, proved to grow the best of the microbes from the lake, although not without changes from their normal development. The cells grown in the arsenic came out about 60 percent larger than cells grown with phosphorus, but with large, empty internal spaces.

By labeling the arsenic with radioactivity, the researchers were able to conclude that arsenic atoms had taken up position in the microbe’s DNA as well as in other molecules within it. Dr. Joyce, however, said that the experimenters had yet to provide a “smoking gun” that there was arsenic in the backbone of working DNA.

Despite this taste for arsenic, the authors also reported, the GFAJ-1 strain grew considerably better when provided with phosphorus, so in some ways they still prefer a phosphorus diet.

http://www.nytimes.com/2010/12/03/science/03arsenic.html?pagewanted=1&_r=1&partner=rss&emc=rss

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Another form of life based on Arsenic?

December 2, 2010
The Arecibo message as sent 1974 from the Arec...

The Arecibo message as sent 1974: image via Wikipedia

The Telegraph  has an eye-catching headline (naturally):

‘Life as we don’t know it’ discovery could prove existence of aliens

But even without the exaggerations and the splash headlines, the possible existence of a form of life intimately connected with Arsenic would have enormous consequences on the definition and abundance of life in the universe and on how to go about searching for extra-terrestrial life.

NASA has sent the internet into a frenzy after it announced an “astrobiology finding” that could suggest alien life exists – even on earth.

The discovery could prove the theory of “shadow” creatures which exist in tandem with our own and in hostile environments previously thought uninhabitable. The “life as we don’t know it” could even survive on hostile planets and develop into intelligent creatures such as humans if and when conditions improve. In a press conference scheduled for tomorrow evening, researchers will unveil the discovery of a microbe that can live in an environment previously thought too poisonous for any life-form to survive.

The bacteria has been found at the bottom of Mono Lake in California’s Yosemite National Park which is rich in arsenic – usually poisonous to life.

Somehow the creature uses the arsenic as a way of surviving and this ability raises the prospect that similar life could exist on other planets, which do not have our benevolent atmosphere. Dr Lewis Dartnell, an astrobiologist at the Centre for Planetary Sciences in London, said: “If these organisms use arsenic in their metabolism, it demonstrates that there are other forms of life to those we knew of. “They’re aliens, but aliens that share the same home as us.”

The Brisbane Times reports:

The US space agency has created a buzz with its announcement of a press conference early tomorrow morning (Australian time) to discuss a scientific finding that relates to the hunt for life beyond the planet Earth.

“NASA will hold a news conference at 2pm EST (6am AEDT) to discuss an astrobiology finding that will impact the search for evidence of extraterrestrial life,” it said on its website.

But Nasa has declined to elaborate further on the topic, other than to say astrobiology is the ”study of life in the universe, including its origin and evolution, where it is located and how it might survive in the future”. The vague announcement has sent the blogosphere in a flurry of speculation about its potential meaning.

Blogger Jason Kottke tipped NASA would announce the discovery of arsenic on Titan, or possibly chemical evidence of bacteria utilising it for photosynthesis.

That speculation was quickly picked up and repeated by a number of other bloggers and internet sites. However Kottke theory has been rebuffed by Alexis Madrigal, senior science writer for The Atlantic, who tweeted that he had read the Science article relating to the Nasa announcement. ”I’m sad to quell some of the @kottke-induced excitement about possible extraterrestrial life. I’ve seen the Science paper. It’s not that,” he tweeted.

The American Association for the Advancement of Science, which publishes the journal in which the research will appear, told ABC News in the US that it had received numerous inquiries about the “mostly erroneous online and/or tabloid speculation about the forthcoming research”.

For NASA TV streaming video and downlink information, visit: http://www.nasa.gov/ntv at 2pm EST today (2nd December).


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