text: Arsenate esters, such as those that would be present in DNA, are generally expected to be orders of magnitude less stable to hydrolysis than corresponding phosphate esters. dAMAs, the structural arsenic analog of the DNA building block dAMP, has a half-life of 40 minutes in water at neutral pH. Estimates of the half-life in water of arsenodiester bonds, which would link the nucleotides together, are as short as 0.06 seconds—compared to 30 million years for the phosphodiester bonds in DNA. The authors speculate that the bacteria may stabilize arsenate esters to a degree by using poly-β-hydroxybutyrate (which has been found to be elevated in "vacuole-like regions" of related species of the genus Halomonas
  ) or other means to lower the effective concentration of water. Polyhydroxybutyrates are used by many bacteria for energy and carbon storage under conditions when growth is limited by elements other than carbon, and typically appear as large waxy granules closely resembling the "vacuole-like regions" seen in GFAJ-1 cells. The authors present no mechanism by which insoluble polyhydroxybutyrate may lower the effective concentration of water in the cytoplasm sufficiently to stabilize arsenate esters. Although all halophiles must reduce the water activity of their cytoplasm by some means to avoid desiccation, the cytoplasm always remains an aqueous environment.