Response to comment on "Arsenic(III) Fuels Anoxygenic Photosynthesis in Hot Spring Biofilms from Mono Lake, California"

Schoepp-Cothenet et al. bring a welcome conceptual debate to the question of which came first in the course of planetary biological evolution, arsenite [As(III)] oxidation or dissimilatory arsenate [As(V)] reduction. However, we disagree with their reasoning and stand by our original conclusion.