Arsenic Bacteria found in Mono Lake, California - GFAJ-1
The first organism that replaces phosphorus with arsenic in its cell components
Republished from a December, 2010 press release by NASA.
GFAJ-1: A New Life Form Based Upon Arsenic?
NASA-funded astrobiology research has changed the fundamental knowledge about what comprises all known life on Earth.
Researchers conducting tests in the harsh environment of Mono Lake in California have discovered the first known
microorganism on Earth able to thrive and reproduce using the toxic chemical arsenic. The microorganism substitutes
arsenic for phosphorus in its cell components.
A New Definition of "Life"
"The definition of life has just expanded," said Ed Weiler, NASA's associate administrator for the Science
Mission Directorate at the agency's Headquarters in Washington. "As we pursue our efforts to seek signs of life
in the solar system, we have to think more broadly, more diversely and consider life as we do not know it."
This finding of an alternative biochemistry makeup will alter biology textbooks and expand the scope of the search
for life beyond Earth. The research is published in this week's edition of Science Express.
The Six Building Blocks of Life are Toppled
Carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur are the six basic building blocks of all known forms of life
on Earth. Phosphorus is part of the chemical backbone of DNA and RNA, the structures that carry genetic instructions for
life, and is considered an essential element for all living cells.
Phosphorus is a central component of the energy-carrying molecule in all cells (adenosine triphosphate) and also the
phospholipids that form all cell membranes. Arsenic, which is chemically similar to phosphorus, is poisonous for most
life on Earth. Arsenic disrupts metabolic pathways because chemically it behaves similarly to phosphate.
New Possibilities for Extraterrestrial Life
"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 in residence at the U.S. Geological
Survey in Menlo Park, Calif., and the research team's lead scientist. "If something here on Earth can do something so
unexpected, what else can life do that we haven't seen yet?"
GFAJ-1 Bacteria Incorporates Arsenic into Cells
The newly discovered microbe, strain GFAJ-1, is a member of a common group of bacteria, the Gammaproteobacteria. In the
laboratory, the researchers successfully grew microbes from the lake on a diet that was very lean on phosphorus, but included
generous helpings of arsenic. When researchers removed the phosphorus and replaced it with arsenic the microbes continued to
grow. Subsequent analyses indicated that the arsenic was being used to produce the building blocks of new GFAJ-1 cells.
The key issue the researchers investigated was when the microbe was grown on arsenic did the arsenic actually became incorporated
into the organisms' vital biochemical machinery, such as DNA, proteins and the cell membranes. A variety of sophisticated
laboratory techniques was used to determine where the arsenic was incorporated.
The team chose to explore Mono Lake because of its unusual chemistry, especially its high salinity, high alkalinity, and high
levels of arsenic. This chemistry is in part a result of Mono Lake's isolation from its sources of fresh water for 50 years.
The results of this study will inform ongoing research in many areas, including the study of Earth's evolution, organic chemistry,
biogeochemical cycles, disease mitigation and Earth system research. These findings also will open up new frontiers in microbiology
and other areas of research.
Alternative Biochemistries for Life
"The idea of alternative biochemistries for life is common in science fiction," said Carl Pilcher, director of the NASA Astrobiology
Institute at the agency's Ames Research Center in Moffett Field, Calif. "Until now a life form using arsenic as a building block was
only theoretical, but now we know such life exists in Mono Lake."
The Research Team and Funding Sources
The research team included scientists from the U.S. Geological Survey, Arizona State University in Tempe, Ariz., Lawrence
Livermore National Laboratory in Livermore, California, Duquesne University in Pittsburgh, Pennsylvania, and the Stanford Synchroton Radiation
Lightsource in Menlo Park, California.
NASA's Astrobiology Program in Washington contributed funding for the research through its Exobiology and Evolutionary Biology
program and the NASA Astrobiology Institute. NASA's Astrobiology Program supports research into the origin, evolution, distribution, and future of life on Earth.
Image of GFAJ-1 grown on arsenic. Image by Jodi Switzer Blum, USGS.
NASA leaders and researchers discuss the recent discovery of a bacteria that can subsitute arsenic for phosphorus in its cellular structure at Mono Lake, California.
Some islands in Mono Lake were built by recent eruptions of lava and cinder and by uplift caused by rising magma beneath the lake. Negit Island is less than about 2,000 years old. Three separate vents each erupted individual dacite lava flows to form three parallel elongate flows. The vents are located on the highest parts of the flows. The lava flows erupted between about 2,000 and 200 years ago. USGS caption and image by R.A. Bailey.
