A bacterium trained to substitute arsenic for phosphorus—one of six elements considered essential for life—in some of its basic cellular functions is stirring widespread, high profile coverage.
On Monday, a cryptic NASA press release about the research—embargoed by the journal Science until Thursday afternoon—led to wild speculation about the discovery of life beyond Earth. What the new finding actually suggests, as a well done Nature News article put it, is “the possibility of a biochemistry very different from the one we know, which could be used by organisms in post or present extreme environments on Earth, or even on other planets.”
The arsenic-munching microbe has quickly grown into a major media story. In a column criticizing the “aliens” speculation that was posted Wednesday, while the Science paper was still under embargo, I cautioned that it was an “interesting piece of research, but certainly not one that is bound to make the front page, or perhaps any page.” Allow me to eat my words. The New York Times, The Washington Post, and the San Francisco Chronicle all fronted the news. The Wall Street Journal put it on page three and USA Today on page four.
In retrospect, the high-profile coverage is deserved. Scientists have long believed that all life needs hydrogen, oxygen, carbon, nitrogen, sulfur, and phosphorous to survive, and the discovery of a microbe that can eat arsenic and incorporate it into its cellular structure could upend that basic understanding of nature. Unfortunately, a lot of the coverage has still been faulty and overblown.
A prime example was a Gizmodo story posted Thursday on the usually dependable Wired Science blog. “Hours before its special news conference today, the cat is out of the bag,” the lede read. “NASA has discovered a completely new life form that doesn’t share the biological building blocks of anything currently living on planet Earth. This changes everything.”
In fact, the bacterium that was coaxed into the arsenic-phosphorous substitution was collected from Mono Lake in California and shares all the same building blocks as other life. The faulty Gizmodo article aroused the ire of science journalist David Dobbs, who runs the blog Neuron Culture at Wired Science. In an effort to push it farther down on the website’s home page, Dobbs penned a post highlighting examples of more accurate coverage.
The discovery is amazing, but it’s easy to go overboard with it. For example, this breathlessly hyperbolic piece, published last year, suggests that finding such bacteria would be “one of the most significant scientific discoveries of all time”. It would imply that “Mono Lake was home to a form of life biologically distinct from all other known life on Earth” and “strongly suggest that life got started on our planet not once, but at least twice”.
The results do nothing of the sort. For a start, the bacteria - a strain known as GFAJ-1 - don’t depend on arsenic. They still contain detectable levels of phosphorus in their molecules and they actually grow better on phosphorus if given the chance. It’s just that they might be able to do without this typically essential element - an extreme and impressive ability in itself.
Nor do the bacteria belong to a second branch of life on Earth - the so-called “shadow biosphere” that Wolfe-Simon talked about a year ago. When she studied the genes of these arsenic-lovers, she found that they belong to a group called the Oceanospirillales. They are no stranger to difficult diets. Bacteria from the same order are munching away at the oil that was spilled into the Gulf of Mexico earlier this year. The arsenic-based bacteria aren’t a parallel branch of life; they’re very much part of the same tree that the rest of us belong too.
That doesn’t, however, make them any less extraordinary.