Annoying Arsenic Claim Debunked for Good - We Hope.

It didn’t make sense from the get-go. A group of researchers claimed last December that they’d discovered an arsenic-based life form. They made a bunch of noise about a “shadow biosphere” that might have sprung from a separate origin of life. There was also a bunch of hand-waving about how this also had something to do with life on other planets. And someone said it could lead to new fertilizer. 

It was one of those annoying press conferences in which the scientist spent all her time telling the world how important her finding was and no time explaining what the evidence was to back the claim. 

Well, the only part that’s holding together now is the fact that there was enough BS dished out to fertilize the whole Midwest. Now scientists have also shot down the scientific claim that the organisms can exist without phosphorus and that they make special DNA that substitute arsenic for phosphorus. It was published online in Science, the same journal that published the initial findings.

As soon as I started reporting on the findings last December I found a number of serious doubters, including one who compared the claim with cold fusion. Here’s a passage from one previous story:

On Thursday, the researchers issued a more modest claim. Instead of saying the microbes had completely substituted arsenic for phosphorus, a new statement says the arsenic replaced "a small percentage" of the phosphorus. A number of biologists say they'll be surprised if even this stands the test of time.
The claims "do not follow from their results," said Simon Silver, a University of Illinois microbiologist who specializes in heavy-metal resistance in bacteria. "This conclusion is not merited from what they did and measured and I think it most likely is a mistake and should never have been claimed or published."
The findings were published in the journal Science, which also issued the researchers' latest statement. Most of its 16 pages were responses to critics.
At the original NASA news event, the team leader, Felisa Wolfe-Simon, had been vague about how much arsenic had substituted for phosphorus, but several times she implied that arsenic had replaced all the phosphorus in the bacterial DNA and other crucial biological molecules.
"All life requires carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur," she said. "I've shown here today that we've discovered a life-form that substitutes arsenic for phosphorus in its DNA. . . . It's solved the challenge of being alive in a very different way."
NASA reinforced this notion with an animated graphic of a DNA molecule, in which little orange balls representing phosphorus magically disappeared and were all replaced by green balls representing arsenic....Some have compared the hype surrounding the arsenic bacteria to a 1996 NASA announcement of possible fossilized Martian bacteria in a meteorite.
Silver says this latest claim is worse. To its credit, he said, the Mars meteorite team had been clearer about separating its evidence from its conclusions.
"Here they claim far-out conclusions without supporting results. It is more like Uri Geller spoon-bending and 'water with memory' and 'cold fusion,' " he said. read the rest here.

Here’s what Science has to say:

“Two new reports show that a bacterium, known as GFAJ-1, requires small amounts of phosphate to grow -- and that it cannot substitute arsenic for phosphorus to survive, as one previous report had suggested. The GFAJ-1 bacterium, found in the arsenic-rich sediments of California's Mono Lake, became the center of a controversy last year when researchers reported that the microorganism could incorporate arsenic into its DNA when phosphorus wasn't available. But Tobias Erb and colleagues now show that, although GFAJ-1 is able to grow under high-arsenate and low-phosphate conditions, the bacterium needs to be supplied with some amount of phosphate in order to grow at all…. Phosphorus remained essential for the organisms to grow, although GFAJ-1 was able to grow a t much lower phosphate concentrations than other arsenate-resistant strains, they say. Read the paper here.