Fig. 3.

Distribution of 13 arsenic detoxification genes among strict anaerobes and aerobes. Species were classified either as aerobes (including facultative anaerobes) or anaerobes based on their capability to use oxygen as a terminal electron acceptor. Each black tick indicated the presence of the corresponding gene in a taxon. Genes evolved before or at beginning of GOE were denoted as blue, and those after as green. Oxygen-dependent genes (arsI and arsH) were indicated with the star symbol.