The GFAJ-1 bacteria, grown on arsenic
In a press conference held today, scientists working with
NASA announced the discovery of a new microorganism right here
on Earth that employs a survival strategy never seen before in
any other life form. Found in Northern California’s
highly-saline Mono Lake, the GFAJ-1 bacteria exists in an
environment that has very little phosphorous, an element that
had previously been considered essential for all living things
in order to build DNA. To cope with this problem, the bacteria
is able to substitute highly-toxic arsenic for phosphorous, in
its cell components. The fact that a microbe is able to survive
in such a fashion opens up the possibilities for where life
could exist on other planets, and will require a rethink on
NASA’s part regarding its search for extraterrestrial life
forms.
Until this announcement, it had been assumed that carbon,
hydrogen, nitrogen, oxygen, phosphorus and sulfur were required
for any terrestrial organism to grow. Phosphorous is considered
to be an essential part of the backbone of DNA and RNA. Arsenic,
on the other hand, is highly poisonous to most life forms – it
is, however, chemically-similar to phosphorous.
Felisa Wolfe-Simon, a NASA Astrobiology Research Fellow in
residence at the U.S. Geological Survey, led a team that first
discovered GFAJ-1 in the salty, alkaline mud of Mono Lake. Mud
from the lake was taken back to her lab, and placed in a medium
that (like the lake) had very little phosphorous, but lots of
arsenic. The bacteria was observed growing in the mud, despite
everything. When analyzed, the
GFAJ-1 were found to be using the arsenic as
phosphorous.
“What I’ve presented to you today is a microbe, doing
something different than life as we knew it,” said Wolfe-Simon.
“We’ve cracked open the door to what’s possible for life
elsewhere in the universe, and that’s profound.”
“I find this result delightful, because it makes me have to
expand my notion of what environmental constituents might enable
habitability,” added Pamela Conrad, of NASA’s Jet Propulsion
Laboratory. “We still don’t know everything there is to know
about what might make a habitable environment on another
planet.”
The research was published today in the journal
Science.
All images courtesy NASA.
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