two days ago, NASA announced "a discovery in astrobiology that will have a major impact on the search for evidence of extraterrestrial life." Were fired speculation about the possible content of that announcement, coming to join the possibility that investigators had found U.S. space agency finally irrefutable evidence some form of life beyond Earth, perhaps in Titan, the largest moon of Saturn. NASA's discovery, however, does not come from any planet or satellite remote. Has occurred here on Earth, though no less spectacular. It is a strange new creature, a new form of "being alive" that challenges everything we thought we knew so far about the complicated and sensitive biochemical process known as life. Something that will completely change the way in which, from now on, look for living beyond our own world.
from bacteria to whales, flies, elephants or humans, each and every one of the ways life on Earth depends on a careful combination of these six elements: oxygen, carbon, hydrogen, nitrogen, phosphorus and sulfur. In the form of DNA, fats and proteins, these elements are found in every living creature known. The "chemistry of life" is also very sensitive and specific than any alteration in this "silver bullet" affects the molecular stability to the point of making life simply no longer possible. So the discovery is published today in the journal Science has caused so much excitement and surprise. Because this is an exception, the first facing the science, to this rule so far considered as universal. Arsenic
to grow
Researchers have indeed found a bacterial strain, the GFAJ-1, which has proven to be able to substitute in their molecules, including DNA, one of six key ingredients, phosphorus , which is considered one of the worst and most harmful poisons that exist, the arsenic. Something that, according to scientists, is a proof that life can develop very different from those we know. Ways to help us refine the existing search techniques for life beyond our planet.
"Life," reads the Science article, is mainly composed the elements carbon, hydrogen, nitrogen, oxygen, sulfur and phosphorus. But despite these six elements are nucleic acids, proteins and fats, and therefore most of living matter, it is theoretically possible that some other elements of the periodic table can perform the same functions. Here we describe a bacterium, strain GFAJ-1 of Halomonadaceae obtained at Mono Lake in California, which has replaced arsenic-phosphorus to sustain growth. Our data reveal the presence of arsenate in macromolecules typically contain phosphates and, notably, nucleic acids and proteins. The replacement of a major bioelements may have a large geochemical and evolutionary significance.
Alternatives to life
For several years, the principal author of this article, Felisa Wolfe-Simon, the Astrobiology Institute NASA in Menlo Park, California, along with some other of the signatories, as Ariel Anbar and Paul Davies, were exploring the possibility that there are "alternative forms" of life. "Life as we know," says Anbar requires some elements specific chemicals and excludes others. But are these the only options? How different life can be? "Wolfe-Simon and his colleagues sensed that arsenic could be replaced to match (the next element in the periodic table) in the earliest life forms on our planet. In fact, arsenic has chemical properties similar to those of phosphorus, although its high toxicity can not use the vast majority of living beings.
However, Wolfe-Simon speculated that some kind of bacteria were able to adapt to the use of arsenic. One idea widely criticized because of this element compounds (arsenates) are much more volatile than the phosphates in the presence of water, a difficulty that no living cell would be able to handle.
To test their ideas, Wolfe-Simon decided to collect California mud lake (Mono Lake), a veritable desert of water ", known for its high concentrations of arsenic, and cultivate the microorganisms obtained in solutions increasingly rich arsenates. The researcher did not add phosphates to the breeding grounds at any time. Rather, it was regularly transferring bacteria to solutions increasingly rich in compounds of arsenic, to wind down any natural concentration of phosphate that may contain your samples. So that bacteria, if they wanted to survive, would be forced to use crop arsenic.
A huge surprise
itself Wolfe-Simons says, in essence, not expecting to find anything alive at the end of the experiment. And that was shocked when he saw through the microscope, colonies of bacteria moving rapidly in that medium as toxic. To be sure, the culture revisited for possible traces of phosphorus that would have helped the bacteria to survive. Not found. So, with the rest of his team, began to discuss in detail the bacteria, to see if, indeed, were using arsenic to survive. "It contained breathing during each of these tests," says the researcher. The results confirmed
their suspicions. The bacteria were incorporated arsenic in place of phosphorus in nucleic acids in their lipids, their protein ... DNA analysis of bacteria left no doubt: it contained arsenic. Paul Davies explained that "this body has a dual capacity. It can grow both phosphorus and arsenic, which makes it very peculiar." For this research, the new agency "has the potential to open a whole new branch of studies in microbiology."
"Our findings," says Simon Wolfe meanwhile, are a reminder that life as we know it could be much more flexible than asuminos or we can imagine. "However, cocluye-this is not a story about arsenic and Mono Lake. If there is anything here on Earth, capable of doing something so unexpected, what other things we have not seen yet is capable of making life? It's time to find out. "(ABC)
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