FIG 6.

Phylogenetic tree based on the amino acid sequence of 41 large subunits of type 1 [NiFe] hydrogenases from diverse phyla, including “Ca. Udaeobacter” sp. (indicated with a red diamond). The red branches of the neighbor-joining tree indicate the high-affinity hydrogenase type 1h as also classified by HydDB. All other subclasses of type 1 [NiFe] hydrogenases are noted at the respective brackets. Bootstrap values of ≥50 calculated based on 500 iterations are shown at the branching points, and the bar represents 0.20 changes per amino acid position. All positions with less than 90% site coverage were eliminated.