Currently the mainstream opinion is that the bacteria didn't use arsenate, but were very good at using the small amounts of phosphate that was still present in the experiment. And that the experimenters were not very good at cleaning all the phosphate out of the growth medium.
So the highly publicized 2010 study is now pretty much falsified.
So the highly publicized 2010 study is now pretty much falsified.
http://www.nature.com/news/arsenic-life-bacterium-prefers-ph...
https://en.wikipedia.org/wiki/GFAJ-1#Criticism