Variation in the composition and abundance of hydrogenase enzyme homologs encoded among 68 publicly available community metagenomes from serpentinization-influenced environments. a) Non-metric multidimensional scaling (NMDS) ordination of the hydrogenase profiles among 68 metagenomes, as predicted using the METABOLIC platform (described in supplementary methods). Points are colored according to the pH of the environment from where the metagenome derives, as indicated by the scale to the right. b) the total fraction of all hydrogenase orthologs relative to the total encoded proteins of a metagenome. Points are shown in relation to the pH of the environment from where the metagenome derives, with the system of origin indicated by color.