In 2010, NASA announced that research led by Dr. Felisa Wolfe-Simon, then a fellow with NASA's astrobiology program, found a strain of bacterium in California's Mono Lake that could substitute arsenic for phosphorus in its DNA.
This discovery caused a flutter in the scientific community as it meant there were organisms which could survive extreme environments and raised hopes of there being a possibility of existence of life beyond Earth.
Two papers published Sunday in the prestigious journal Science show how the bacterium, identified as GFAJ-1, is able to grow at low phosphate concentrations even in the presence of high concentrations of arsenate. However, the organism lacks the ability to grow in phosphorus-depleted arsenate-containing medium. GFAJ-1 is considered to be an arsenate-resistant, phosphate-dependent strain.
Another paper published on the same topic and authored by Marshall Louis Reaves, Rosemary J. Redfield, Sunita Sinha, Joshua D. Rabinowitz and Leonid Kruglyak noted that GFAJ-1 does not replace phosphorus with arsenic throughout its DNA, but sometimes assimilates arsenate in small amounts in the place of phosphate.
Six elements are considered as essential building blocks of life. They are carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur. Though arsenic has properties similar to phosphorus, it is poisonous for living organisms.
The NASA announcement in 2010 followed several experiments conducted at California's Mono Lake, which possesses an unusually high concentration of salt with high levels of arsenic and minerals and reflects conditions similar to when life evolved on earth.
Scientist Rosemary Redfield did not stop with just publishing the paper disputing the claim, she also vented her feelings in a blog stating, 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.
The recent findings indicate that the bacterium is a well-adapted organism that lives in a high-arsenic environment.
In a report published in Mercury News, microbiologist Wolfe-Simon, currently working with Lawrence Berkeley National Laboratories, stands by her work. She said that arsenic may not have been detected by the opponents as it degraded once the bacteria were sliced open for study.
If the new findings stand the test of time, they can become a major embarrassment for NASA.
Meanwhile, Wolfe-Simon and her team continue to study the organism's resistance to arsenic poisoning and its ability to integrate with the toxic element. A new paper from the Wolfe-Simon team is expected to be published in a few months.