Figure 2.

Phylogenetic trees showing the diversity of the human colonic hydrogenases. The trees represent the protein sequences of the [FeFe]-hydrogenase catalytic domains (A) and [NiFe]-hydrogenase catalytic subunits (B) derived from the genomes of human colonic microorganisms. The trees were constructed by the neighbor-joining method, are bootstrapped with 500 replicates, and are color -coded by hydrogenase class.