Arsenic Based Life at Mono Lake

This arsenic strain arosenaturally through phosphorous replacement in the lab and was then shown to havealso occurred in Mono Lake were similarconditions existed.  The obviousconclusion is that replacement experiments should be run for all likely alternativechemistries.

It was certainly unexpected, butwidens life’s envelope of adaptability into far more chemically hostileconditions. Clearly slow shifts in chemistry give the bacteria the time to testout successful replacement protocols that they can exploit.  This is a level of adaptability that wassurprising.

As I have posted, bacterial lifewill find a life zone on just about any planet. It just will not be our life zone. I have little doubt now that the balance of probability is heavily weightedfor life on every planet in the solar system now.  We have plenty of evidence that life carryingmaterial is out in space and such material can deliver living spores.

The adaptation to arsenic and alsosurely antimony as the two are totally similar and annoy miners no end letslife operate in mineral rich hydrothermal environments associated with hotspots.

We also now have a new protocolthat can explore cellular variability for a range of environmentalmodifications for a wide range of unlikely and even unnatural chemicalprotocols.

Arsenic life

Dec. 2, 2010:  NASA-supportedresearchers have discovered the first known microorganism on Earth able tothrive and reproduce using the toxic chemical arsenic. The microorganism, whichlives in California's Mono Lake,substitutes arsenic for phosphorus in the backbone of its DNA and other cellularcomponents.

"The definition of life has justexpanded," said Ed Weiler, NASA's associate administrator for the ScienceMission Directorate at the agency's Headquarters in Washington. "As we pursue our effortsto seek signs of life in the solar system, we have to think more broadly, morediversely and consider life as we do not know it."

This finding of an alternative biochemistrymakeup will alter biology textbooks and expand the scope of the search for lifebeyond Earth. The research is published in this week's edition of ScienceExpress.

Carbon, hydrogen, nitrogen, oxygen, phosphorusand sulfur are the six basic building blocks of all known forms of life onEarth. Phosphorus is part of the chemical backbone of DNA and RNA, thestructures that carry genetic instructions for life, and is considered anessential element for all living cells.

Phosphorus is a central component of theenergy-carrying molecule in all cells (adenosine triphosphate) and also thephospholipids that form all cell membranes. Arsenic, which is chemicallysimilar to phosphorus, is poisonous for most life on Earth. Arsenic disruptsmetabolic pathways because chemically it behaves similarly to phosphate.

"We know that some microbes can breathearsenic, but what we've found is a microbe doing something new -- buildingparts of itself out of arsenic," said Felisa Wolfe-Simon, a NASAAstrobiology Research Fellow in residence at the U.S. Geological Survey inMenlo Park, Calif., and the research team's lead scientist. "If somethinghere on Earth can do something so unexpected, what else can life do that wehaven't seen yet?"

The newly discovered microbe, strain GFAJ-1,is a member of a common group of bacteria, the Gammaproteobacteria. In thelaboratory, the researchers successfully grew microbes from the lake on a dietthat was very lean on phosphorus, but included generous helpings of arsenic.When researchers removed the phosphorus and replaced it with arsenic themicrobes continued to grow. Subsequent analyses indicated that the arsenic wasbeing used to produce the building blocks of new GFAJ-1 cells.

The key issue the researchers investigated waswhen the microbe was grown on arsenic did the arsenic actually becameincorporated into the organisms' vital biochemical machinery, such as DNA,proteins and the cell membranes. A variety of sophisticated laboratorytechniques was used to determine where the arsenic was incorporated.

The team chose to explore Mono Lakebecause 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'sisolation from its sources of fresh water for 50 years.

The results of this study will inform ongoingresearch in many areas, including the study of Earth's evolution, organicchemistry, biogeochemical cycles, disease mitigation and Earth system research.These findings also will open up new frontiers in microbiology and other areasof research.

"The idea of alternative biochemistriesfor life is common in science fiction," said Carl Pilcher, director of theNASA Astrobiology Institute at the agency's Ames Research Center in MoffettField, Calif. "Until now a life form using arsenic as a building block wasonly theoretical, but now we know such life exists in Mono Lake."

The research team included scientists from theU.S. Geological Survey, Arizona State University in Tempe, Ariz., LawrenceLivermore National Laboratory in Livermore, Calif., Duquesne University inPittsburgh, Penn., and the Stanford Synchroton Radiation Lightsource in MenloPark, Calif.

NASA's Astrobiology Program in Washington contributed funding for the researchthrough its Exobiology and Evolutionary Biology program and the NASAAstrobiology Institute. NASA's Astrobiology Program supports research into theorigin, evolution, distribution, and future of life on Earth.

Editor: Dr. Tony Phillips | Credit: Science@NASA

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