Felisa Wolfe-Simon, a young NASA astrobiologist, has always been was fascinated by crustaceans because they don’t use iron to carry oxygen around in their bodies the way most species do. Instead, they use copper. She wondered if this kind of chemical substitution could go even further and still support life.
“What about the main building blocks of life? Carbon, hydrogen, nitrogen, oxygen, phosphorous and sulphur — can we substitute any of those? And the dogma is no,” she said. But researchers and scientists being the inquisitive people they are, Wolfe-Simon started thinking about phosphorous and the element just below it on the periodic table: arsenic.
“Arsenic is toxic because it looks like phosphorous,” she said, “so your cells and my cells and microbial cells can’t tell the difference.” Until they ingest arsenic and they die. But she thought that evolution has created such an immense diversity of creatures, many of which live in toxic environments, so she set out looking for an environment that was naturally toxic with arsenic.
The environment she picked is Mono Lake in California. It’s a very odd lake …very salty and very, well arsenicky! Yet the lake is teeming with microscopic life in its muddy lake bed.
So Wolfe-Simon scooped up a some mud off the floor of the lake and brought it back to her lab and put it in a liquid where arsenic was added but no phosphorous. When she put a sample of the mud under her microscope she found some “fast-swimming little bugs in there.” A few more tests showed her that arsenic had even replaced some of the phosphorous in the organism’s DNA. What should have killed the organism made it thrive! This was no spider from Mars but a little alien critter right here on Earth!
NASA lost no time in hailing this as a landmark discovery. If an essential building block for life can be replaced by another so poisonous, then there are chances of finding such deadly mixes outside of the earth that could support life.
So far the little critter has been dubbed the GFAJ-1 strain, but really it should be given a rock star name. Maybe David Bowie can help?