NASA's "Mono Lake Discovery": What Did They Really Find?
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December 02, 2010

NASA's "Mono Lake Discovery": What Did They Really Find?

Mono Lake, California

An arsenic-eating bacterium offers hope for life living on alien worlds, NASA scientists suggested Thursday. Reported in the journal Science, by a team led by Felisa Wolfe-Simon of the NASA Astrobiology Institute in Menlo Park, Calif., who has been conducting reserach at Mono Lake California for years and led the experiment, the Halomonadaceae bacterium turned up in a survey of the salty and arsenic-rich Mono Lake.

"Biological dependence on the six major nutrient elements carbon, hydrogen, nitrogen, oxygen, sulfur, and phosphorus is complemented by a selected array of other elements, usually metal(loid)s present in trace quantities that serve critical cellular functions, such as enzyme co-factors. There are many cases of these trace elements substituting for one another," says the study. "However, there are no prior reports of substitutions for any of the six major elements essential for life. Here we present evidence that arsenic can substitute for phosphorus in the biomolecules of a naturally-occurring bacterium."

The scientists said that they had trained a bacterium taken from the bottom of Mono Lake in California 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 unknown alien biochemical powers.

The bacterium, and grown for months in a lab mixture containing arsenic, gradually replaced atoms of phosphorus as its energy source for atoms of arsenic. Phosphorus is one of six chemical elements that have long been thought to be essential for all life on Earth until now. The others are carbon, oxygen, nitrogen, hydrogen and sulfur.

Phosphorus chains are the backbone building block of DNA and its chemical bonds, particularly in a molecule known as adenosine triphosphate, the principal means by which biological creatures store energy.

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, reports The New York Times "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."

Scientists said the results, if confirmed, would dramatically extend our understanding 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 in an interview with The New York Times. “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 told the New York Times, “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 added, but about “cracking open the door and finding that what we think are fixed constants of life are not.”

Arsenic sits right beneath phosphorus in the periodic table of the elements and shares many of its chemical properties -a 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."

The Viking landers that failed to find life on Mars in 1976, Dr. Wolfe-Simon pointed out, were designed before the discovery the discovery of Earth's extremophiles such as of tube worms and other weird life at deep undersea vents and the ancient dry valleys and buried lakes of Antarctica.

Evidence of possible life on Mars sent back from by two Mars Viking Landers in 1976 and 1977 was inconclusive, at least according the then primitive knowledge of both extreme life that we now know exists on Earth as well as the abundant existence of water and methane on Mars past and present.

Mars_methane_map On Mars, as on Earth, methane is extremely unstable because it's continually being broken up by ultraviolet rays from the Sun and chemical reactions with other gases. The average life of a methane molecule on Mars is 400 years, which means the gas must be continually replenished or it will disappear. Something is producing methane on Mars today -the big question is: What?

A new study indicates that methane in the atmosphere of Mars lasts less than a year. Methane is replenished from localized sources that show seasonal and annual variations. This pattern of methane production raises questions as to whether the methane comes from geological activity - or biological processes. The atmosphere on Mars consists of 95% carbon dioxide, 3% nitrogen, 1.6% argon, and contains traces of oxygen and water, as well as methane.

Sergio Fonti (Universita del Salento) and Giuseppe Marzo (NASA Ames) have used observations from NASA’s Mars Global Surveyor spacecraft to track the evolution of the gas over three martian years..

“Only small amounts of methane are present in the martian atmosphere, coming from very localized sources. We’ve looked at changes in concentrations of the gas and found that there are seasonal and also annual variations. The source of the methane could be geological activity or it could be biological -- we can’t tell at this point. However, it appears that the upper limit for methane lifetime is less than a year in the martian atmosphere,” said Fonti.

Levels of methane are highest in autumn in the northern hemisphere, with localized peaks of 70 parts per billion, although methane can be detected across most of the planet at this time of year. There is a sharp decrease in winter, with only a faint band between 40 and 50 degrees north. Concentrations start to build again in spring and rise more rapidly in summer, spreading across the planet.

“One of the interesting things that we’ve found is that in summer, although the general distribution pattern is much the same as in autumn, there are actually higher levels of methane in the southern hemisphere. This could be because of the natural circulation occurring in the atmosphere, but has to be confirmed by appropriate computer simulations,” said Fonti.

“It’s evident that the highest concentrations are associated with the warmest seasons and locations where there are favorable geological -- and hence biological -- conditions such as geothermal activity and strong hydration. The higher energy available in summer could trigger the release of gases from geological processes or outbreaks of biological activity,” said Fonti.

“Our study is the first time that data from an orbiting spectrometer has been used to monitor methane over an extended period. The huge TES dataset has allowed us to follow the methane cycle in the martian atmosphere with unprecedented accuracy and completeness. Our observations will be very useful in constraining the origins and significance of martian methane,” said Fonti.

Methane was first detected in the martian atmosphere by ground based telescopes in 2003 and confirmed a year later by ESA’s Mars Express spacecraft. Last year, observations using ground based telescopes showed the first evidence of a seasonal cycles.

There is potentially a vast biosphere a few meters below Mars' surface, which the 1976 Viking mission may not have been able to access since it was only scratching the surface of the uppermost layer of soil.

NASA's first press release about the Viking tests announced that the results were positive. The "labeled Release" (LR) experiments had given positive results. But after lengthy discussions in which Carl Sagan participated, NASA reversed its position, mainly because another experiment detected no organics in the soil.

Yet to this day,  Gilbert Levin, the principal designer of the LR experiment, believes the tests pointed to life. When the same two experiments were run on soil from Antarctica, the same conflicting results were obtained (LR - positive; organics - negative.) Soil and ice from Antarctica's Dry Valley certainly contains extreme life forms. The test for organics was negative because it is far less sensitive than the LR experiment. The same problem could have caused the organics test on to give a false negative.

Before oxygen could accumulate in Earth's atmosphere, all the exposed iron had to rust. During that process, lasting hundreds of millions of years, Earth was also a red planet. In the journal Nature, Corinna Wu asked: Could the oxygen that rusted the iron on have been produced biologically? Could life on Mars have simply "run out of steam" after that stage of its development?
 
In a paper in The International Journal of Astrobiology, Felisa Wolfe-Simon  and Ariel Anbar and Paul Davies, both of Arizona State University, predicted the existence of arsenic-loving life forms.

According to the article in Science, 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 along with large, empty internal spaces.

By labeling the arsenic with radioactivity, the NASA Astrobiology 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. It was inconclusive, however, that there was arsenic in the backbone of working DNA.

Casey Kazan via The New York Times and Science

Comments

Pfft...I'm underwhelmed. We were all worked up about some really important thing on exobiology, and all they came up with is some bug that eats arsenic instead of getting killed by it. The actual not-getting-killed-by-arsenic part has, oh, I don't know, been known for 20 odd years or so...
Just do an ordinary google search on extremophiles in chemically polluted areas, like in Russia or nuclear waste facilities.

The big difference is that they found arsenic as part of the internal biochemical processes, as in, its building blocks of life.

I would like to point out that even though arsenic has been shown to be attached to DNA now, it hasn't actually been shown to be part of the actual genetic DNA. DNA is sometimes used as part of a protein or other chemically active microstructure.

This is an essential difference, because the actual DNA that encodes for life always holds phosphorus. It is essential for its existence.

Unless the NASA scientists have actually found arsenic-based DNA coding the life of that specific bacteria, they have not made a big discovery.
Now if they DID find an actual DNA-like code that used arsenic instead of phosphorus, they would have discovered a totally alien and incompatible form of life. There can be no question of intermixing these two DNA-forms, unless the arsenic-DNA lifeform still holds the chemical codes for using phosphorus-DNA. This is not unthinkable, but has not been shown.

If you had followed the search for extremophiles of the past 30 years or so, you would have known it was only a matter of time a lifeform would be discovered that used arsenic.

The fact that, because it is so close to Phosphorus in the table of elements makes it poisonous to most life, because it will be interfering with all the biochemical functions that use phosphorus. However, it will also mean that, chemically speaking, there is only a small evolutionary gap to bridge before using arsenic as a substitute for phosphorus.

The mere fact that NASA is acting like they reinvented the wheel while all they did was finally finding something that had been expected for 20 years, only serves to show they got very little imagination.

Seriously, I was expecting something like the spectroscopic discovery of some very complex organic compound (like chlorophyl or some other protein) on Mars or Titan or so, or the discovery of liquid water on some outer-planet moon. This is small stuff.

"The beauty of the living thing is not the atoms that go into it. ... But the way those atoms are put together." - Carl Sagan

Carl may have been the smartest human that ever lived. :)

This was a smoke screen to distract attention from the wikileaks scandal.

All I can say is.. Bah, Humbug!... What will NASA discover next? Hot Water? This is nothing new of a discovery, they're called extremophiles and have been discovered a long time ago(lookup the iron extremophiles)... I wonder what they'll try next for some attention... Maybe they'll blow up the Space Shuttle? They have to compete with Jersey Shore you know... just for the ratings..lol. Let's face it nobody cares about NASA these days, but it's their own fault, they used to go to the moon, now they spend money funding these highschool science projects

hi, i'm another idiot who doesn't really care about or understand the study of astrobiology. this post is similar to the others posted as i am a moron, and will criticize many things i don't fully comprehend.

Generally I do not post on blogs, but I would like to say that this post really forced me to do so, Excellent post!

It's funny how we adopt words and adapt our lexicon to the times. This is a very useful slant on things.

That is an awfully astounding column you've posted.Thanks a lot for that a fantastically amazing post!

That is an awfully astounding column you've posted.Thanks a lot for that a fantastically amazing post!

"The scientists said that they had trained a bacterium taken from the bottom of Mono Lake in California to eat and grow on a diet of arsenic..."

They didn't train the bacterium- and Felcia made this clear in the conference- they harvested the microbe from the lake and put it in an arsenic-rich, zero-phosphorous growth medium to confirm it's properties. It was already doing the arsenic thing- no need to "train".

http://www.nasa.gov/topics/universe/features/astrobiology_toxic_chemical.html

Actual news item

And could somebody put an IP-ban on the bot with all the weird hats above? TIA

A discovery of middling import used as a career-booster for one very obnoxious member of the tribe. Did anyone else watching the news conf feel like they were suddenly being read to in some SoCal preschool at "story time"? I don't need anything named "Wolfe-Simon" telling me what is profound. But it was priceless comic relief, I am grateful to NASA for that.

I wonder what would be NASA next discovery to their lovely GFAJ-1?
Really amazing if any other gas can substitute nitrogen, which is really very minor on Mars to breathe.

Thanks for your sharing!
http://www.likehats.com

hi, that was narly dudes! Is this "MONO" like mononucleosis?

Are aliens real? wat is the next discovery/


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