Vertical gradients of gene families or groups of functionally related gene families enriched in the oxic zone (A), anoxic (high H₂S) zone (B) and varying across the oxic–anoxic border (low H₂S) zone (C). Relative abundance is normalized by the average number of genes in a layer. In most cases, these genes and groups of genes were over-represented relative to other metagenomic data sets (Table I). Error bars denote standard deviations calculated from 1000 bootstrap resamplings of predicted proteins, and points with non-overlapping error bars are treated as significantly different. Lists of gene families used in each group (Photosynthesis-related proteins, Chaperones, Ferredoxins and associated proteins, Sugar degradation pathways, Chemotaxis and Flagella) as well as details of the resampling procedure are given in Supplementary information.

Average isoelectric point (A) and aspartate content (B) of all predicted proteins in the mat layer communities and reference bacteria, archaea, phages and microbiomes available through IMG/M (Markowitz et al, 2006). Genomic average was computed for each genome or microbiome, with 10 layers of the mat treated separately. These values were rounded up to the next (larger value) bin in increments of 0.2 and 0.5 in (A) and (B) respectively, and the distribution of the bins was plotted as a fraction of each data set.

Isoelectric point profiles of predicted proteins (A) and GC content profiles of reads (B) for mat layer communities. In (A), isoelectric point profiles for selected reference genomes are added to highlight the highly overlapping and acid-shifted mat layer profiles.