Carbon fixation pathways encoded in the genomes. (A) Alluvial diagram showing the phylum-level classification of the 67 strains possessing key genes for each carbon fixation pathway. (WL) Wood–Ljungdahl pathway; (roTCA) reversed oxidative tricarboxylic acid cycle; (rTCA) reverse tricarboxylic acid cycle; (CBB) Calvin–Benson–Bassham cycle. (B) Presence of key genes for each carbon fixation pathway in the genomes of the four autotrophic strains highlighted in the box. (*) A gene for RuBisCO form III, but not forms I or II, was detected in the genome of Pyrodictium brockii JCM 9392^T (for details, see the main text). (CCS) Citryl-CoA synthetase; (CCL) citryl-CoA lyase; (ACL) ATP-citrate lyase; (CODH) carbon monoxide dehydrogenase; (ACS) acetyl-CoA synthase; (PRK) phosphoribulokinase; (Rbc) ribulose-bisphosphate carboxylase; (CS) citrate synthase; (OFOR) 2-oxoacid:ferredoxin oxidoreductases; (MDH) malate dehydrogenase.