A salt-loving (halophilic) bacterium which can grow in medium containing arsenic instead of phosphorus has been selected from the microbial community of Mono Lake in California. Arsenic (As) is a chemical analog of phosphorus and is usually toxic because it can enter metabolic pathways in the place of phosphorus. It appears to be incorporated into macromolecules of the bacterium (called GFAJ-1) that normally contain phosphorus, such as nucleic acids and proteins. The identification of bacteria that can utilize arsenic has many metabolic and evolutionary implications. I’m wondering whether there are viruses that infect bacteria such as GFAJ-1.