The reported discovery of a bacterial strain able to use arsenic in place of phosphorus to make essential molecules such as DNA generated much controversy and has recently been refuted. Murray Deutscher and his colleagues at the University of Miami in Florida provide an alternative explanation for the puzzling observation that bacteria of the strain Halomonadaceae GFAJ-1 grow when supplied with arsenate instead of phosphate.
The researchers used a radioactive isotope to label ribosomes — the cell's protein-making machinery — in the bacterium Escherichia coli. They found that arsenate causes ribosomes to degrade, a process that releases phosphate. After being cultured for about 80 hours in media that contained arsenate but not phosphate, a few arsenate-tolerant E. coli cells began to grow, slowly. Rather than growing by replacing phosphorus with arsenic, these cells recycled phosphorus released by deteriorating ribosomes, the authors suggest.
J. Biol. Chem. http://dx.doi.org/10.1074/jbc.C112.394403 (2012)