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Courtesy: Jodi Switzer Blum

If bacteria can rely on arsenic, rather than phosphorous to grow, the way scientists understand life could change dramatically.

Arsenic debate refuses to die

by Brian Warmoth
May 27, 2011

NASA researchers shook up the biology world last December when they proposed that a bacterium could grow when given arsenic instead of phosphorous.

The paper, authored by NASA researcher Felisa Wolfe-Simon and published in the journal Science, challenged long-held beliefs that phosphorous is an essential building block for life. Moreover, it opened up a public discussion about a potential new life form.

Now, six months after bloggers and scientists began raising concerns over Wolfe-Simon’s methods and results, she confronted critics head on in a technical response published by ScienceXpress. Some skeptics among eight formal comments published on Science's website remain unpersuaded that phosphorous was sufficiently eliminated from the study.

Wolfe-Simon, meanwhile, hopes to further discussion by addressing concerns and making bacterium samples available to the scientific community.

"We didn't set out to be renegades,” Wolfe-Simon said. “We didn't set out to change paradigms."

Simply put, she wanted to find out if there could there be a microbe that could sustain itself when given a lot of arsenic and not a lot phosphorous. The paper earned her a spot on Time’s 2011 list of “the most influential people in the world,” and it placed her work under worldwide scrutiny.

Zoologist and blogger Rosemary Redfield, for instance, has been an outspoken critic of the initial paper, titled “A Bacterium That Can Grow by Using Arsenic Instead of Phosphorus.” Redfield, a professor at the University of British Columbia in Vancouver, expressed doubts early on regarding phosphorous contamination and cleaning practices and presented her case in one of the responses.

She stated that contamination may have been an issue and introduced enough phosphorous to ruin the samples of bacterium, called GFAJ-1. Wolfe-Simon and her team asserted that more phosphorous would have been need.

"We argue that it's still not enough," Wolfe-Simon said.

The NASA group’s technical response included more background information about its methods, including some phosphate amounts and steps in their DNA/RNA extraction procedure.

"Overall, I think the scientific criticisms still stand," Redfield said.

And Redfield is not alone. Researcher Stefan Oehler from the Biomedical Sciences Research Center Alexander Fleming in Vari, Greece, contended that Wolfe-Simon’s conclusions still remain uncertain.

Redfield also questioned why it took six months for Wolfe-Simon and her colleagues to respond in detail to critiques.

Wolfe-Simon maintained that those months have been spent evaluating questions and reaching conclusions through scientific research. In that time, she has also been working to make GFAJ-1 samples available to other researchers, who wish to perform their own studies.

"What wasn't viewable to the general public were all of the emails for people looking to collaborate with us," she explained. According to Wolfe-Simon, emails expressing support were approximately equal to those casting doubt on her findings.

In the end, she accepts ongoing research and debate as a part of science, but elevating issues in biology and microbiology into popular discussion makes her feel like she is doing her job.

“The public is engaged and that is incredible,” she said.