8/4/2019 0. Arsenic Life Test
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Felisa Wolfe-Simon has been criticized for her work on bacteria
recovered from an arsenic-rich lake.
M I C R O B I O L O G Y
Will you take thearsenic-life test?Critiques prompt researchers
to offer samples of poison-
tolerant microbe to doubters.
B Y E R I K A C H E C K H A Y D E N
At first, it sounded like the discovery ofthe century: a
bacterium that can sur-
vive by using the toxic element arsenicinstead of phosphorus in
its DNA and in otherbiomolecules.
But scientists have lined up to criticize theclaim since it
appeared in Science six monthsago1. Last week, the journal
published a volleyof eight technical comments29 summarizingthe key
objections to the original paper, along
with a response from the authors10, who standby their work.
The authors of the original paper are alsooffering to distribute
samples of the bacterium,GFAJ-1, so that others can attempt to
repli-cate their work. The big question is whetherresearchers will
grab the opportunity to testsuch an eye-popping claim or, as some
arealready saying, they will reject as a waste oftime the chance to
repeat work they believe isfundamentally flawed. I have not found
any-body outside of that laboratory who supportsthe work, says
Barry Rosen of Florida Inter-national University in Miami, who
published
an earlier critique of the paper11.
Some are also frustrated that the authorsdid not release any new
data in their response,despite having had ample time to
conductfollow-up experiments of their own to bolstertheir case. Im
tired of rehashing these pre-liminary data, says John Helmann of
CornellUniversity in Ithaca, New York, who critiquedthe work in
January on the Faculty of 1000website12. I look forward to the time
whenthey or others in the field start doing the sortof rigorous
experiments that need to be doneto test this hypothesis.
The original study1, led by Felisa Wolfe-Simon, a NASA
astrobiology research fellowat the US Geological Survey in Menlo
Park,California, looked at bacteria taken from thearsenic-rich Mono
Lake in southern Califor-nia. The authors grew the bacteria in
their labusing a medium that contained arsenic butno phosphorus.
Even without this essentialelement of life, the bacteria reproduced
andintegrated arsenic into their DNA to replace
the missing phosphorus,the paper reported.
We maintain thatour interpretation of As
[arsenic] substitution,
based on multiple congruent lines of evidence,is viable,
Wolfe-Simon and her colleagueswrote in last weeks response10.
But critics have pointed out that the growthmedium contained
trace amounts of phos-phorus2,3 enough to support a few roundsof
bacterial growth5. They also note that theculturing process could
have helped arsenic-
tolerant bacteria to survive by killing off lesswell-equipped
microbes3.Others say that there is simply not enough
evidence that arsenic atoms were incorporatedinto the bacteriums
DNA4, 69. The chemicalinstability of arsenate relative to
phosphatemakes this an extraordinary claim that wouldset aside
nearly a century of chemical dataconcerning arsenate and phosphate
mol-ecules, writes Steven Benner4 of the Foun-dation for Applied
Molecular Evolution inGainesville, Florida.
A leading critic of the work, Rosemary Red-field of the
University of British Columbia in
Vancouver, Canada, says that it would be rela-tively
straightforward to grow the bacteria inarsenic-containing media and
then analysethem using mass spectrometry to test whetherarsenic is
covalently bonded into their DNAbackbone.
Redfield says that she will probably get sam-ples of GFAJ-1 to
run these follow-up tests, andhopes that a handful of other
laboratories willcollaborate to repeat the experiments
indepen-dently and publish their results together.
But some principal investigators are reluc-tant to spend their
resources, and their stu-dents time, replicating the work. If
youextended the results to show there is no detect-able arsenic,
where could you publish that?asks Simon Silver of the University of
Illinoisat Chicago. How could the young person whowas asked to do
that work ever get a job?
Helmann says that he is in the process ofinstalling a highly
sensitive mass spectrometerthat can measure trace quantities of
elements,which could help refute or corroborate thefindings. But
the equipment would be betteremployed on original research, he
says. Ivegot my own science to do.
1. Wolfe-Simon, F.et al.Science doi:10.1126/science.1197258
(2010).
2. Foster, P. L. Science doi:10.1126/science.1201551
(2011).3. Redfield, R. J. Science doi:10.1126/science.1201482
(2011).
4. Benner, S. A. Science doi:10.1126/science.1201304 (2011).
5. Cotner, J. B. & Hall, E. K. Science
doi:10.1126/science.1201943 (2011).
6. Schoepp-Cothenet, B. et al. Science
doi:10.1126/science.1201438 (2011).
7. Csabai, I. & Szathmry, E. Science
doi:10.1126/science.1201399 (2011).
8. Oehler, S. Science doi:10.1126/science.1201381(2011).
9. Borhani, D. W. Science doi:10.1126/science.1201255
(2011).
10. Wolfe-Simon, F.et al.Science doi:10.1126/science.1202098
(2011).
11. Rosen, B. P., Ajees, A. A. & McDermott, T.
R.BioEssays33, 350357 (2011).
12. Helmann, J. F1000.com/6854956 (2011).
H.
BORTMAN
NATURE.COM
For a longer versionof this story see:
go.nature.com/oaetjq
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