Asking About Arsenic

Geomicrobiologist Felisa Wolfe-Simon, collecting lake-bottom sediments in the shallow waters off Mono Lake’s 10 Mile Beach. Credit: ©2010 Henry Bortman

On December 2, NASA held a press conference to announce the discovery of a bacterium from California’s Mono Lake that has a novel biochemistry. The research article that described this finding, published in the journal Science, provided several lines of evidence that suggested the bacterium can substitute arsenic for a small percentage of its phosphorus and sustain its growth.

The finding made headlines around the world. Life uses six elements — carbon, oxygen, hydrogen, nitrogen, sulfur and phosphorus – to construct important molecules such as nucleic acids (DNA), proteins and lipids. The discovery of a bacterium that could replace phosphorus with arsenic indicates, according to NASA, that alternative chemistries for life is possible, and therefore increases the likelihood that life exists elsewhere in the universe.

“We know that some microbes can breathe arsenic, but what we’ve found is a microbe doing something new — building parts of itself out of arsenic," said Felisa Wolfe-Simon, a NASA astrobiology research fellow in residence at the U.S. Geological Survey in Menlo Park, Calif., and the research team’s lead scientist. "If something here on Earth can do something so unexpected, what else can life do that we haven’t seen yet?" 

Rosie Redfield, a blogger who runs a microbiology research lab in the Life Sciences Centre at the University of British Columbia, posted a review online that was highly critical of the research presented in the Science paper. This blog posting, which has become a center point of debate about the study, provided a detailed examination of the research and the flaws she perceived in it.:

“Basically, [the paper] doesn’t present ANY convincing evidence that arsenic has been incorporated into DNA (or any other biological molecule),” Redfield wrote.

Ron Oremland and Felisa Wolfe-Simon collect samples of lakeshore mud from Mono Lake’s 10-Mile Beach. Credit: ©2009 Henry Bortman

Read Redfield’s review here:

The controversy about the NASA research and the media’s response to it was the topic of a panel discussion at a meeting of the American Geological Union held in San Francisco this week. Ron Oremland, one of the co-authors of the Science paper, was a member of the panel and discussed the history that led up to the discovery.

The scientists behind the original study have now posted a response to the criticism, with this note:

“The best science opens up new questions for us as a community and sparks the interest and imagination of the general public. As communicators and representative of science, we feel that support of new ideas with data is critical but also to generate new ideas for others to think about and bring their talents to bear on. We look forward to working with other scientists, either directly or by making the cells freely available and providing DNA samples to appropriate experts for their analyses, in an effort to provide more insight into this intriguing finding.”

Their response to the criticism of the arsenic life paper is outlined here: