1. 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 Similarity 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. Coph. Corr = 0.8371

2. 0.960.90.840.780.660.60.54 0.72 Similarity 0.90.80.70.60.50.40.30.20.1 Similarity (A)(B) 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. Coph. Corr = 0.7694Coph. Corr = 0.9828

3. 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 B C 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. (A) 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 C (A)