All life on Earth - from microbes to elephants and us - is based on a single genetic model that requires the element phosphorus as one of its six essential components.
But now researchers have uncovered a bacterium that has five of those essential elements but has, in effect, replaced phosphorus with its look-alike but toxic cousin arsenic.
The discovery the door to that possibility and to the related existence of a theorized "shadow biosphere" on Earth - life evolved from a different common ancestor than all that we've known so far.
"Our findings are a reminder that life-as-we-know-it could be much more flexible than we generally assume or can imagine," said Felisa Wolfe-Simon, the young biochemist who led the effort after being selected as a NASA Astrobiology Research Fellow and as a member of the National Astrobiology Institute team at Arizona State University.
"If something here on Earth can do something so unexpected - that breaks the unity of biochemistry - what else can life do that we haven't seen yet?" she said.
The research, funded through NASA and conducted with samples from California's Mono Lake, found that some of the bacteria not only used arsenic to live, but had arsenic embedded into their DNA, RNA and other basic underpinnings.
"This is different from anything we've seen before," said Mary Voytek, senior scientist for NASA's program in astrobiology , the arm of the agency involved specifically in the search for life beyond Earth and for how life began here.
"These bugs haven't just replaced one useful element with another, they have the arsenic in the basic building blocks of their makeup," she said. "We don't know if the arsenic replaced phosphorus or if it was there from the very beginning - in which case it would strongly suggest the existence of a shadow biosphere." source -read more
A few news presentations on the conference
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