Fig. 2.

Anaerobic respiration processes. a Reconstruction of selected respiratory pathways: denitrification, sulfate reduction, and methanogenesis. The normalized absolute abundances of the genes catalyzing each step are given in the respective cells. b Taxonomic annotation of the metagenomic reads associated to the mcr gene. The seven most abundant orders are shown; each of the remaining orders represented less than four reads in the samples. Enzyme names: narGHI/napAB, nitrate reductase; nirS/nirK, nitrite reductase; norBC, nitric oxide reductase; nosZ, nitrous oxide reductase; sat, sulfate adenylyltransferase; aprAB, adenylylsulfate reductase; dsrAB, dissimilatory sulfite reductase; fwdABCD/fmdBC, formylmethanofuran dehydrogenase; ftr, formylmethanofuran-tetrahydromethanopterin N-formyltransferase; mch, methenyltetrahydromethanopterin cyclohydrolase; mtd, methylenetetrahydromethanopterin dehydrogenase; mer, 5,10-methylenetetrahydromethanopterin reductase; mtrABCDEFGH, tetrahydromethanopterin S-methyltransferase; mcrABG, methyl-coenzyme M reductase