Fig. 3.

Methanogenic community structure. Relative OTU distributions of mcrA genes retrieved in construction of clone libraries from digesters D37, D^TE37, D42 and D^TE42 at day 280 (period 3) based on 99 % identity threshold. Figures in the sectors represent OTU numbers. OTU1 and OTU19 had low identity (<79 %) to previously available mcrA genes. Nucleotide/amino acid sequence identity/similarity (%) to M. bourgensis OTU2: 92/89; OTUs 3–9: 97–99/≥89; OTU20: 92/89. Sectors with similar colour but different tunes are OTUs assembling based on 97 % identity threshold and referred to as assemblage A (blue), B (red) and C (green). Uncoloured sectors are OTUs and single mcrA genes with relatively low abundance. Frequencies and identities of the OTUs are listed in Additional file 1: Table S1