ON THE CUTTING EDGE: Arsenic And New Lifeforms
The theory of abiogenesis postulates that the chemicals present in the Earth's primordial atmosphere - methane (CH4), ammonia (NH3), water (H2O), hydrogen sulfide (H2S), carbon dioxide (CO2) or carbon monoxide (CO), and phosphate (PO43-) - gave rise to organic molecules, which in turn organized to form more complex structures and then evolved into increasingly advanced life forms. Thus, the biochemistry of life on Earth generally depends upon six elements, carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur, with the vast majority of organisms using carbon as a building block for basic cellular structures and functions and water as a solvent. But the silicate skeletal structure of diatoms and sulfur-reducing bacteria suggest the possibility that
the biochemistry of alien lifeforms could rely on other elements and solvents. And now, on our own planet NASA astrobiologists have found a microbe unlike any other, making the probability of the existence of alien lifeforms more plausible. Agence France-Press reports:
Bacteria that thrive on arsenic have been scooped from a California lake, a discovery that redefines the building blocks of life and offers new hope in the search for other organisms on Earth and beyond.
Not only do the bacteria survive, they grow by swapping phosphorus for arsenic in their DNA and cell membranes, said the study funded by the US space agency NASA and published Thursday in the journal Science. …
"What we've found is a microbe doing something new - building parts of itself out of arsenic," said scientist Felisa Wolfe-Simon, a fellow in NASA's astrobiology program who made the groundbreaking discovery at Mono Lake in eastern California.
"There's an organism on Earth doing something different," said Wolfe-Simon. "We've cracked open the door to what's possible for life elsewhere in the universe. And that's profound."
Michael New, NASA's astrobiology discipline scientist, tells Astrobiology Magazine that the discovery of an organism with arsenate DNA indicates that “expands our understanding of the conditions under which life can thrive, and possibly originate, thereby increasing our understanding of the distribution of life on Earth and the potential habitats for life elsewhere in the solar system."
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