Life on Arsenic?


Life found on...California (photo from NASA)

By now, you’ve probably heard about the “alien” arsenic bacteria discovered in a California lake…and if you’ve been following the story closely, you might have a neck ache from all the twists and turns. When word of a NASA press conference on “astrobiology” broke last week, many hoped that the first evidence of extraterrestrial life was about to be released. But then the news turned out to be the discovery of a bacteria that can grow using the poisonous element arsenic, not little green men. But wait – the substitution of arsenic for phosphate (one of the key six ingredients for life) at least meant that the rules for life had been rewritten, still a cool finding. But wait again!

Over the weekend, scientists began lining up to take chunks out of the Science paper containing the findings from NASA and US Geological Survey scientists. First, microbiologist Rosie Redfield dissected the methodology of the paper and found it considerably lacking, if not intentionally deceptive. Science writer Carl Zimmer followed with damning comments from several scientists supporting Redfield’s take and adding more fuel to the fire…even going so far as to say that the paper should not have been accepted by a journal and published. And even more writers piled on with critiques of how NASA and Science promoted the research, and how media outlets handled the science. It’s all very confusing.

One interested observer is Jack Gilbert, assistant professor of ecology & evolution at the University of Chicago and an environmental microbiologist at Argonne National Laboratory. Gilbert uses genetic and computational techniques to study microbial function and diversity in their natural environments, a field where an arsenic-based bacterial species would be big-time news. But Gilbert finds the paper far less momentous than some of the original, breathless coverage.

“This is just another example of a microbe that has found a niche that enables it to survive in areas where other microbes would not be able to survive,” Gilbert said in a phone interview yesterday. “Bacteria are incredibly versatile, that’s all this paper is really saying.”

503457main_arsenic_fullA resistance to the poisonous effects of arsenic would be helpful for the bacteria, called GFAJ-1 (pictured at right), to survive in its natural habitat of Mono Lake, where arsenic levels are extremely high. But the experiments published in Science don’t look at GFAJ-1 in its natural environment, but rather in the laboratory, where researchers artificially removed the element phosphate (used in building DNA and many important proteins) and replaced it with increasing levels of arsenic. The big finding was that this inhospitable environment did not kill the bacteria – and at some arsenic concentrations, it could actually grow and reproduce, purportedly by building DNA and proteins with arsenic instead of phosphate.

One of Redfield’s main objections is that the treatments used in these experiments probably didn’t remove all of the phosphate, and trace amounts left behind could have allowed the bacteria to survive with no novel biological tricks. Gilbert said he hadn’t yet read Redfield’s post, but agreed that he would have requested the authors run more experiments and controls to shore up their conclusions. But now that the paper has been published, he agrees with the authors when they say that the proper forum for criticism is through the peer-reviewed journals.

“As an impatient person, I find peer review incredibly frustrating, but it’s there for a very good reason,” Gilbert said. “Peer review enables us to question the findings in other research articles, and that’s essential if we want to figure out if the piece of work isn’t up to scratch.”

Until then, the debate will remain in the media…well, the science blogging community, at least. Gilbert said he doesn’t think that the story would have kicked up nearly as much media dust if it hadn’t been for the false rumors about extraterrestrial life, but considers the momentary mainstream interest in bacteria to be a teachable moment about the Earth’s microbes and their many wonders yet to be discovered.

“The very fact the press is now interested in bacteria again – albeit for the wrong reasons – is an opportunity to educate the public about importance of these systems,” Gilbert said. “Microbes have been around for 3.5 billion years, we’ve only been around 200,000. There’s an awful lot they can teach us.”

About Rob Mitchum (525 Articles)
Rob Mitchum is communications manager at the Computation Institute, a joint initiative between The University of Chicago and Argonne National Laboratory.
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