FIG 4.

Distribution of autotrophic pathways and regulons in Crenarchaeota. The phylogenetic species tree was constructed using the concatenated alignment of 78 universal bacterial proteins in the MicrobesOnline database (http://www.microbesonline.org/cgi-bin/speciesTree.cgi). P. arsenaticum lacks the key enzyme of the pathway, 4hbd; however, despite the fact that its DHC pathway is incomplete, P. arsenaticum was reported to be able to grow chemolithoautotrophically with carbon dioxide as a carbon source.