posted 12-02-2010 08:53 AM               

NASA Sets News Conference on Astrobiology Discovery

NASA will hold a news conference at 2 p.m. EST on Thursday, Dec. 2, to discuss an astrobiology finding that will impact the search for evidence of extraterrestrial life. Astrobiology is the study of the origin, evolution, distribution and future of life in the universe.

The news conference will be held at the NASA Headquarters auditorium at 300 E St. SW, in Washington. It will be broadcast live on NASA Television and streamed on the agency's website.

Participants are:

• Mary Voytek, director, Astrobiology Program, NASA Headquarters, Washington
  
• Felisa Wolfe-Simon, NASA astrobiology research fellow, U.S. Geological Survey, Menlo Park, Calif.
  
• Pamela Conrad, astrobiologist, NASA's Goddard Space Flight Center, Greenbelt, Md.
  
• Steven Benner, distinguished fellow, Foundation for Applied Molecular Evolution, Gainesville, Fla.
  
• James Elser, professor, Arizona State University, Tempe

posted 12-02-2010 11:48 AM               

All living organisms on this planet use six elements for almost all of the chemical structures of DNA, RNA, proteins, and lipids. There is a smattering of other elements, mostly metals, that are essential for biological functions (e.g., the iron in hemoglobin). However, we wouldn’t expect to find anything outside of carbon, hydrogen, oxygen, nitrogen, sulfur and phosphorus in the basic structures of biomolecules. Surprisingly, a team of scientists provide evidence in Science that another element, arsenic, can be incorporated into the basic chemical makeup of the macromolecules of life, replacing some of its phosphorus.

Evolutionary geochemist Felisa Wolfe-Simon, the lead author, and her colleagues found a strain of bacterium (GFAJ-1 of the Halomonadaceae family) that can grow in a medium abundant in arsenic and lacking phosphorus. The GFAJ-1 bacterium naturally resides in the arsenic-rich waters (200 uM) of Mono Lake located in California's Eastern Sierra, and it belongs to a family of proteobacteria that is known to accumulate arsenic. It's not remarkable that GFAJ-1 survives in high concentrations of arsenic, but what is startling is that it potentially integrates arsenic into its DNA and proteins.

posted 12-02-2010 11:52 AM               

NASA's secret is finally out: Researchers say they've forced microbes from a gnarly California lake to become arsenic-gobbling aliens. It may not be as thrilling as discovering life on Titan, but the claim is so radical that some chemists aren't yet ready to believe it.

If the claim holds up, it would lend weight to the idea that life as we know it isn't the only way life could develop. Organisms with truly alien biochemistry could conceivably arise on a faraway exoplanet, or on the Saturnian moon Titan, or even here on Earth.

"Our findings are a reminder that life as we know it could be much more flexible than we generally assume or can imagine," Felisa Wolfe-Simon, an astrobiology researcher at the U.S. Geological Survey, said in a statement from Arizona State University announcing the results. Wolfe-Simon is the lead author of a paper reporting the findings, which was published online today by the journal Science.

posted 12-02-2010 05:15 PM               

NASA-Funded Research Discovers Life Built With Toxic Chemical

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.

"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.

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.

"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?"

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 were 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.

"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 included scientists from the U.S. Geological Survey, Arizona State University in Tempe, Ariz., Lawrence Livermore National Laboratory in Livermore, Calif., Duquesne University in Pittsburgh and the Stanford Synchrotron Radiation Lightsource in Menlo Park.

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.

posted 07-09-2012 09:03 AM               

The original study, funded by NASA, was led by biologist Felisa Wolfe-Simon, now of the Lawrence Berkeley (Calif.) National Laboratory, and co-authored by other federal researchers.

Wolfe-Simon and colleagues had suggested that the microbe, discovered at California's Mono Lake, "can vary the elemental composition of its basic biomolecules by substituting (arsenic) for (phosphorus)," an extraordinary claim that was essentially based on growing the bug in test tubes with the phosphorus seemingly removed. Tests suggested the bug was incorporating arsenic in places usually reserved for phosphorus, including genetic material, a result considered impossible in theory.

Theory looks to have been correct. In the new studies, one headed by Julia Vorholt of Switzerland's ETH Zurich university and the other by Rosemary Redfield of Canada's University of British Columbia, researchers tested the bug, provided by Wolfe-Simon and colleagues, and both found that while it can survive amid high arsenic concentrations, it needs some low level of phosphorus to grow. Further, they found the bug did not incorporate arsenic into its genetic chemistry.

The "new research shows that GFAJ-1 does not break the long-held rules of life," says the editorial statement by Science. The bacteria, "is likely adept at scavenging phosphate under harsh conditions, which would help to explain why it can grow even when arsenic is present within the cells," it says.

Wolfe-Simon says in response, "There is nothing in the data of these new papers that contradicts our published data." Her team hopes to submit more data on the microbe for publication within a few months, she suggests.