Dec 2, 2010

There are several species of bacteria, especially GFAJ-1, which can live on arsenic. A new study reported on Science today found that phosphorus might be replaced by arsenic in the building block, including DNA, in these bacteria. It is known that phosphorus along with oxygen, hydrogen, carbon, nitrogen, and sulfur are the basic six elements of life on earth. Arsenic, 33, in some respect, similar to phosphorus , 32, on periodic table, but it is toxic to multicellular life including human through interacting with thiol groups of proteins. Why arsenic is not toxic to bacteria like GFAJ-1 is yet to be determined. Should these bacteria be called a new genesis or a new variant? One thing is clear that phosphorus, although preferred, could be replaced in a few of earth life. In synthetic oligo DNA, phosphorus could be replaced by sulfur in DNA backbone. It is yet to be determined whether and how arsenic replaces phosphorus in DNA backbone.