Metabolic predictions for Melainabacteria based on genes identified in Figure 4—source data 1. Genes in pathways detected in the genomes of the subsurface and at least one gut genome (white box), only in the subsurface genome (grey box), only in at least one gut genome (orange box), and genes missing from pathways in all genomes (red box). Glycolysis proceeds via the canonical Embden-Meyerhof-Parnas (EMP) pathway with the exception of fructose-6-phosphate 1-phosphotransferase (EC:22.214.171.124, gene 3). Names of pathways and fermentation end-products are bolded and ATP generated by substrate-level phosphorylation are noted. All Melainabacteria genomes sampled lack electron transport chain components (including cytochromes (Cyto), succinate dehydrogenase (sdh), flavins, quinones), terminal respiratory oxidases or reductases, and photosystem I or II (PS1, PS2). The genomes also lack a complete TCA cycle (absent enzymes noted by red boxes), with the TCA enzymes instead linked to the fermentation of amino acids and organic acids denoted (pathways, blue arrows). Ferredoxin (Fd, green text) is important for hydrogen (H2) production via hydrogenases (yellow background box). Proton translocation mechanisms (green background box) may be achieved by the activity of trimeric oxaloacetate (OAA) decarboxylase and sodium-hydrogen antiporter, pyrophosphate (PPi) hydrolysis with pyrophosphatases, 11 subunit NADH dehydrogenase, and an annotated NiFe hydrogenase (green enzyme). Annotations for the gene numbers are in Figure 4—source data 2. The complete metabolic comparison of the Melainabacteria can be accessed at http://ggkbase.berkeley.edu/genome_summaries/81-MEL-Metabolic-Overview-June2013.