July 10, 2012
New Study Disproves Claims About Bacteria Thriving On Arsenic
Lee Rannals for redOrbit.com - Your Universe Online
Scientists have disproved a 2010 NASA study regarding how some bacterial life can thrive on arsenic.The journal Science said that new research shows the original 2010 controversial study results did not match up to the new findings.
"Contrary to an original report, the new research clearly shows that the bacterium, GFAJ-1, cannot substitute arsenic for phosphorus to survive," said a statement by the U.S. journal.
The same peer-reviewed magazine published the initial study in December 2010, with researchers announcing that a new form of life had been scooped from a California lake.
The bacterium found in Mono Lake was said to redefine the building blocks of life, because lead researcher Felisa Wolfe-Simon said the bacterium survived despite having arsenic in its DNA and cell membranes instead of phosphorus.
Biologists consider the six elements necessary for life to be carbon, hydrogen, nitrogen, oxygen, phosphorous and sulphur.
Arsenic is similar to phosphorous, but is known to be poisonous to living organisms.
The original study needed to be confirmed in order to be considered a discovery, and two separate teams found that the bacterium needed some phosphate in order to survive, therefor it could not fully survive on arsenic alone.
NASA conducted numerous studies at eastern California's Mono Lake because the area is thought to reflect conditions similar to what would be found on Mars, or in early life on Earth, due to its unusually salty body of water with high arsenic and mineral levels.
The original study members acknowledged there were very low levels of phosphate within their study samples, and concluded that this was a level of contamination that was insufficient to permit the bacterium to grow.
However, two separate articles published in Science now reveal that the Wolfe-Simon and her colleagues medium did contain enough phosphate contamination to support the growth of the bacterium, according to the statement.
One of the papers found that the bacterium was not really replacing phosphorus with arsenic throughout its DNA, but "may sometimes assimilate arsenate into some small molecules in place of phosphate."
"I don't know whether the authors are just bad scientists or whether they're unscrupulously pushing Nasa's 'There's life in outer space!' agenda," Rosemary Redfield at the University of British Columbia wrote in a blog that ignited the web furore shortly after the paper was first published.
The other paper found that the bacterium still needed phosphorus in order to survive, despite the bacterium being able to live in a high-arsenic environment.
Scientists described the bacterium as "a well-adapted extremophile that lives in a high-arsenic environment."
It "is likely adept at scavenging phosphate under harsh conditions, which would help to explain why it can grow even when arsenic is present within the cells," said the journal's statement.
"The scientific process is a naturally self-correcting one, as scientists attempt to replicate published results," it added.
The journal did not retract the original study, but said it was "pleased to publish additional information" on the bacterium.