Still, the team acknowledges that this strong preference for phosphates can allow some arsenic compounds to enter the cell.
For all the flack they've taken for their initial paper, Dr. Wolfe-Simon, with the Lawrence-Berkeley National Laboratory, and colleagues are continuing to probe the workings of GFAJ-1.
The Nature study has "helped us understand molecular-level discrimination between arsenate and phosphate" in GFAJ-1 and other microbes, writes Felesia Wolfe-Simon, who led the original study, in an e-mail exchange.
Indeed, the original work revealed arsenic in the cells, adds colleague John Trainer, with the Scripps Research Institute in La Jolla, Calif., and the new work doesn't rule out its migration into the bacteria, "so microbes evidently have multiple levels of adaptation to arsenic."
The team now is focusing its efforts on how the bacteria accommodate arsenic in their cells and live to tell the tale.