Five years ago, the U.S. Geological Survey's Ronald S. Oremland discovered a microbe that can generate energy from arsenic. Now, Oremland has helped a team led by Felisa Wolfe-Simon of the NASA Astrobiology Institute uncover a bacterium that can grow in the presence of either arsenic or phosphorus (Science, DOI: 10.1126/science.1197258).
Living things are largely made of six elements: carbon, nitrogen, hydrogen, oxygen, sulfur, and phosphorus. But some scientists searching for life on other planets or vestiges of early life on Earth think other elements could serve the same functions. When grown in arsenic-rich environments, the new bacterium, a member of the Halomonadaceae family plucked from sediments at California's briny, arsenic-rich Mono Lake, contains arsenic in its proteins, metabolites, and DNA, according to mass spectrometry and X-ray spectroscopy measurements.
The discovery is tantalizing, says Barry P. Rosen, an expert in arsenic and its metabolism at Florida International University. The next step must be to isolate specific molecules in which arsenic is incorporated and show that they're functional, including DNA sequences and major metabolites such as glucose-6-phosphate, he adds.