Life was still life, just as we knew it.

From Science Fictions by Stuart Ritchie.  Page 145.   

In 2010, Science published a paper by researchers at NASA describing a strain of mysterious bacteria living in California’s Mono Lake. The lake is an odd place: not only is the water highly alkaline and around three times as salty as the ocean, but rising above its surface are irregular, stalagmite-like towers of limestone that look to be straight from the set of a science-fiction movie.   It was an apt location for scientists seeking to investigate some of the world’s most exotic species and see what lessons they might teach us about the chemistry of life on other planets. 

 

According to the study, led by the microbiologist Felisa Wolfe-Simon, the bacteria’s adaptation to the lake’s extreme environment had caused two unique things to happen. First, they had grown and multiplied in an environment that contained virtually no phosphorus, one of the elements thought to be essential for all forms of life. Second, and even more sensationally, the reason for the growth was that the bacteria, which Wolfe-Simon named GFAJ-1, had altered the very backbone of their own DNA, replacing the phosphorus with an element abundant in Mono Lake: arsenic. Arsenic is, of “course, well known to be a poison, and this made the result doubly surprising: not only was it unheard of for another element to replace phosphorus in the DNA molecule but arsenic, particularly in such high levels, is usually toxic. Not so, apparently, for GFAJ-1, where arsenic played the opposite role, sustaining its life.  If the results held up, they would do a lot more than ‘Give Felisa a Job’ – which, by the way, is what the bacteria’s name stands for.  They would change the way we thought about life itself. Wolfe-Simon certainly seemed aware of the implications: at a news conference announcing the study, she described how the discovery had ‘cracked open the door to what’s possible for life elsewhere in the universe.’ 

 

Time to tear up the textbooks? Not so fast. From the get-go, other researchers were sceptical about ‘arsenic life’.  The University of British Columbia microbiologist Rosemary Redfield noted flaws in the study and described them in a series of detailed blog posts.  Wolfe-Simon’s response was to disregard the criticism. ‘We’re not going to engage in this sort of discussion,’ she told a journalist. ‘Any discourse will have to be peer-reviewed in the same manner as our paper.’  This seemed a little rich, given that NASA had clearly sought to pique broad public interest when announcing the paper’s publication. A few days beforehand, they’d told the world in a tantalising press release that a new finding ‘will impact the search for evidence of extraterrestrial life.’  It led to a frenzy of speculation: one much-read blog immediately “suggested that signs of life might have been found on Saturn’s largest moon, Titan.  And although the findings, when revealed, weren’t quite that exciting, NASA still managed to frame them in portentous terms. ‘The definition of life has just expanded,’ enthused a NASA administrator immediately after the paper appeared. ‘As we pursue our efforts to seek signs of life in the solar system, we have to … consider life as we do not know it.’
 
Still, it wasn’t long before Wolfe-Simon got her wish and the discussion moved to the journals. In a relatively rare example of a journal publishing strong critiques of one of its previous articles – an example, one might suggest, of the scientific process working just as it should – Science printed no fewer than eight ‘Technical Comments’ on the study, including one by Redfield, along with a defiant response from Wolfe-Simon and her colleagues.  Redfield and her team then put the arsenic-bacteria claims properly to the test.  One of Wolfe-Simon’s main observations had been that whereas the bacteria wouldn’t multiply in an environment that had neither phosphorus nor arsenic, they would when arsenic was added to the mix. Redfield and colleagues attempted but failed to replicate this in their lab: they found that GFAJ-1 didn’t grow at all unless phosphorus was provided. And as far as GFAJ-1’s DNA was concerned, they found only minimal arsenic there after they’d washed the samples in water. The best explanation was a banal one: simple contamination. The arsenic with which Wolfe-Simon fed the bacteria might have been contaminated with enough phosphorus to allow some growth; Wolfe-Simon’s DNA samples, conversely, might have been contaminated with arsenic from the Mono Lake-like environment she had created in her lab. A parallel replication attempt at the Swiss Federal Institute of Technology in Zürich gave closely similar results to Redfield’s, providing the final empirical nail in arsenic-life’s coffin.  Life was still life, just as we knew it.