Figure 3.

Distribution of hydrogenase-encoding genes in human colonic metagenomes. The hydrogenase content of 20 metagenomes derived from the HMP GI metagenome database was determined at a depth of 5 million reads. (A) Probable phylum-level affiliation of hydrogenases detected. This was determined by recording the closest BLAST hit for each read against a databank of 3284 hydrogenase sequences.¹⁹ (B) Number of reads corresponding to each [FeFe]-hydrogenase class. (C) Number of reads corresponding to each [NiFe]-hydrogenase class.