[meteorite-list] NASA-Funded Research Discovers Life Built With Toxic Chemical

[Ron Baalke]

Dec. 02, 2010

Dwayne Brown 
Headquarters, Washington 
202-358-1726 
dwayne.c.brown at nasa.gov 

Cathy Weselby 
Ames Research Center, Moffett Field, Calif. 
650-604-2791 
cathy.weselby at nasa.gov   


RELEASE: 10-320

NASA-FUNDED RESEARCH DISCOVERS LIFE BUILT WITH TOXIC CHEMICAL

WASHINGTON -- 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. 

For more information about the finding and a complete list of 
researchers, visit: 

http://astrobiology.nasa.gov   
	
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