Lord Kloo said:
Those little micro-organisms that NASA found the other day that turn phosphorous into arsenic..
Alright, done some looking into this.
The newly discovered microbe, strain GFAJ-1, is a member of a common group of bacteria, the Gammaproteobacteria.
Phosphorus is the chemical backbone of DNA and RNA, it is a central component of the energy-carrying molecule in all cells (adenosine triphosphate, aka ATP. Hence an ATP inhibitor would be bad.) and also the phospholipids that form all cell membranes. Arsenic, which is chemically similar to phosphorus, is poisonous for most life on Earth. Arsenic disrupts metabolic pathways because chemically it behaves similarly to phosphate.
When researchers removed the phosphorus and replaced it with arsenic the microbes continued to grow. Subsequent analyses indicated that the arsenic was being used to produce the building blocks of new GFAJ-1 cells.
So it seems they don't turn phosphorus into arsenic, they just use it instead. Similar to how you could use oak rather then pine for wooden doors I suppose. But oak isn't toxic to all other known life. Go figure.