0.9

1. 0.7 0.8 0.9 0.6 0.1 0.2 0.3 0.4 0.5 Coph. Corr = 0.8371 Figure S1. Multivariate cluster analyses of the abundance of hydrogenotrophic functional genes from 60 human colon biopsies. Multivariate cluster analysis of acs, fhs, mcrA, and dsrAB gene copies/g across the right colon (RC; red), left colon (LC; green) and rectum (Re; blue) were performed using the Morisita similarity index. Cophenetic correlation coefficient (Coph. Corr) values are shown. Similarity

2. 0.1 0.2 0.3 0.4 0.6 0.7 0.9 0.5 0.8 Figure S2. Multivariate cluster analyses of the dsrA 16S rRNA T-RFLP profiles obtained from 60 colon biopsies. Multivariate cluster analysis of dsrA gene profiles across the right colon (RC; red), left colon (LC; green) and rectum (Re; blue) were performed using Kulczynski (A) and Morisita (B) similarity indices. Cophenetic correlation coefficient (Coph. Corr) values are shown. 0.84 0.78 0.96 0.66 0.9 0.72 0.54 0.6 (A) (B) Similarity Similarity Coph. Corr = 0.7694 Coph. Corr = 0.9828

3. (A) DLC2 ARC2 ALC2 BLC1 BRC2* BRC1* BRe2* BRe1* ARe1 ARC1 ALC1 ELC1 DLC1 CRe1 ELC2 CRe2 DRe1* DRe2* ARe2 ERe1* ERe2* DRC2 CLC2 CRC1 CLC1 CRC2 DRC1 BLC2 DLC2 ELC1* ELC2* DRC1* DRC2* DRe2 DLC1 DRe1 ARe1 ARC1 ALC1 ARC2 ALC2 BLC1 BRC2 BRe2 BRC1 BRe1 BLC2 CRe1 ERe1 CRC2* CRC1* CLC1* CLC2* CRe2 ARe2 ERe2 (B) (A) D B A Re B Figure S3. Multivariate cluster analyses of the Desulfovibrio 16S rRNA T-RFLP profiles obtained from replicate biopsies. Multivariate cluster analysis of Desulfovibrio spp. 16S rRNA gene profiles across the right colon (RC; red), left colon (LC; green) and rectum (Re; blue) were performed from replicate biopsies (<1 cm apart) using Kulczynski (A) and Morisita (B) similarity indices. Cophenetic correlation coefficient (Coph. Corr) values are shown. C C