NASA announced Thursday that it has discovered a bacteria that can use arsenic -- a toxic element previously thought unable to sustain life -- as a building block of its DNA and cellular structure. Scientists say the discovery may broaden our definition of what constitutes life and may revolutionize efforts to find signs of life in other parts of the solar system.
NASA fed microbes found in Northern California's Mono Lake (pictured) a diet with limited amounts of phosphorus and a high proportion of arsenic. Mono Lake, about 120 miles southeast of Lake Tahoe, was chosen for the experiment because it hasn't received fresh water in about 50 years and has relatively high salinity, high alkalinity and high levels of arsenic.
When the scientists entirely removed the phosphorus from its environment, the microbe, called strain GFAJ-1, substituted the chemically similar arsenic and continued to grow, making it the first known life form to be able to grow and reproduce using arsenic, NASA said in a statement Thursday.
"We know that some microbes can breathe arsenic, but what we've found is a microbe doing something new -- building parts of itself out of arsenic," said Felisa Wolfe-Simon, a NASA Astrobiology Research Fellow and lead scientist on the project. "If something here on Earth can do something so unexpected, what else can life do that we haven't seen yet?"
The discovery may reorient how scientists classify life forms, because previously, all known forms of life on Earth used carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur as their primary building blocks. While arsenic is chemically similar to phosphorus, it's poisonous for most organisms.
NASA says the study's results will impact research on subjects such as the Earth's evolution, diseases, microbiology and organic chemistry.
In addition to NASA, scientists from the U.S. Geological Survey, Arizona State University, the Lawrence Livermore National Laboratory, Duquesne University and Stanford University participated in the study.