In brief, a team led by Felisa Wolfe-Simon of the the U.S. Geological Survey in Menlo Park, California, obtained some mud from Mono Lake, California, which has a high concentration of arsenic. They cultured bacteria from the mud and grew them in gradually increasing concentrations of arsenic and also decreased the concentration of phosphorus. Arsenic, which is directly below phosphorus in the periodic table, evidently replaced the phosphorus in the bacteria’s chemistry. The bacteria survived on arsenic, though they grew better on phosphorus. The researchers found phosphorus in the proteins, lipids, and other constituents of the cell, as well as in the DNA. Although not everyone agrees, Wolfe-Simon and her team think that the bacteria actually use the arsenic to grow.
Well, as they say on the Web, IANAB, but the result is precisely what any self-respecting adaptationist would have expected. What is interesting, however, is the empirical result that life can grow without phosphorus, and therefore by inference possibly without other elements that are also considered essential. I never thought otherwise, and in fact recall science-fiction writers from my dim, dark past postulating life based on silicon, which is directly below carbon in the periodic table. Evidently NASA has finally wakened up to such possibilities, since they trumpeted the discovery as “an astrobiology finding that will impact the search for evidence of extraterrestrial life.”