Pennisi, “What Poison? Bacterium Uses Arsenic To Build DNA and Other Molecules”

Today, every body talks about the new paper accepted in Science by NASA scientist Felisa Wolfe-Simon (see fotograph) reported also in Science by Elizabeth Pennisi, “Biochemistry: What Poison? Bacterium Uses Arsenic To Build DNA and Other Molecules,” News of the Week, Science 330: 1302, 3 December 2010.

“From elephants to the bacterium Escherichia coli, all forms of life on Earth depend on the same six elements: oxygen, carbon, hydrogen, nitrogen, phosphorus, and sulfur. In a paper published online by Science, a bacterial strain, GFAJ-1, which replace the phosphorus in its key biomolecules, including DNA, with the legendary poison arsenic, is presented. “This is a very impressive and exciting discovery,” says Barry Rosen, a biochemist at Florida International University in Miami.”

“In 2009, Felisa Wolfe-Simon, a geomicrobiologist based at the U.S. Geological Survey in Menlo Park, California, speculated that some microbes might be able to adapt to using arsenic. To test her hypothesis, Wolfe-Simon collected mud from Mono Lake, California, a desert body of water known for having high arsenic levels, and grew the microorganisms from it in increasing concentrations of arsenate. She was thrilled and surprised when one evening she checked the latest cultures under the microscope and saw fast-moving bacteria. She rechecked the components of the culture media to confirm there were no phosphorus contaminants. Mass spectrometry showed that the arsenic was inside the bacterial cells and not some impurity sticking to the outside of the cell; it is present in the protein, lipid, nucleic acid, and metabolite fractions of the cells, suggesting that arsenic had been incorporated in molecules forming each fraction. They also isolated DNA containing arsenic.”

“Wolfe-Simon speculates that organisms like GFAJ-1, which use arsenic to grow,  could have thrived in the arsenic-laden hydrothermal vent–like environments of early Earth, where some researchers think life first arose, and that later organisms may have adapted to using phosphorus.”

“The problem now is to understand how the DNA and other biomolecules can still function with the arsenic incorporated. There is much to do in order to firmly put this microbe on the biological map.”