<p>Table S3: Operational Taxonomic Units (OTUs; with 95% similarity at the nucleotide basis [52-58]) and representative sequences for the Galathea 3 cruise. </p><p>OTU nifH Representative N (total/unique Closest Cultured Accession E value Taxa Reference Cluster sequence seq.) number 1 III Bacteria; Firmicutes; Clostridia; Clostridium Clostridiales; Clostridiaceae; Kopke et al. GA22030.A.D11 8/5 ljungdahlii CP001666 5.54e-62 Clostridium. (2010) [53] 2 III Bacteria; Proteobacteria; Deltaproteobacteria; Desulfovibrio Desulfovibrionales; Lucas et al. GA04070.B.C8 8/5 salexigens CP001649 6.4e-87 Desulfovibrionaceae; Desulfovibrio (unpublished) 3 I Paenibacillus Bacteria; Firmicutes; Bacillales; Choo et al. GA22030.A.C7 10/8 azotofixans AJ515294 3.77e-64 Paenibacillaceae; Paenibacillus. (2003) [54] 4 I Bacteria; Proteobacteria; Betaproteobacteria; Polaromonas Burkholderiales; Copeland et al. GA15030.A.B5 8/8 naphthalenivorans CP000529 6.33e-106 Comamonadaceae; Polaromonas (unpublished) 5 I Bacteria; Proteobacteria; Alphaproteobacteria; Azospirillum Rhodospirillales; Blaha et al. GA22030.A.G10 47/37 lipoferum AY786992 2.07e-118 Rhodospirillaceae; Azospirillum (2005) [55] 6 I Bacteria; Proteobacteria; Alphaproteobacteria; Azospirillum Rhodospirillales; Shukla GA22075.A.C12 20/17 brasilense GQ161238 5.19e-126 Rhodospirillaceae; Azospirillum (unpublished) 7 I Bacteria; Proteobacteria; Alphaproteobacteria; Rhizobiales; Rhodopseudomonas Bradyrhizobiaceae; Xie et al. GA22030.A.C9 17/16 lichen AB241413 1.59e-151 Rhodopseudomonas (unpublished) 8 I Bacteria; Proteobacteria; Methylosinus Alphaproteobacteria; Rhizobiales; Auman et al. GA04070.B.C9 3/1 trichosporium AF378724 2.69e-123 Methylocystaceae; Methylosinus. (2001) [56] 9 I GA22100.A.H6 22/16 Xanthobacter CP000781 5.02e-119 Bacteria; Proteobacteria; Gilbert et al. autotrophicus Py2 Alphaproteobacteria; (unpublished) Rhizobiales;Xanthobacteraceae; Xanthobacter 10 I Bacteria; Proteobacteria; Betaproteobacteria; Burkholderiales; Burkholderiaceae; Burkholderia Burkholderia; Burkholderia cepacia Izumi GA16030.A.G1 39/39 vietnamiensis AM110707 3.27e-160 complex. (unpublished) 11 I Bacteria; Proteobacteria; Ideonella Betaproteobacteria; Noar & Buckley GA04070.B.A3 265/124 dechloratans EU542578 7.70e-143 Burkholderiales; Ideonella. (2009) [57] 12 I Bacteria; Proteobacteria; Alphaproteobacteria; Rhizobiales; Bradyrhizobium sp. Bradyrhizobiaceae; Nzoue et al. GA17030.A.D3 73/58 ORS391 FJ347449 1.00e-147 Bradyrhizobium. (2009) [58] 13 I Bacteria; Proteobacteria; Gammaproteobacteria; Vibrionales; Wommack et al. GA09100.A.A11 83/75 Vibrio diazotrophicus AF111110 1.32e-95 Vibrionaceae; Vibrio. (unpublished) 14 I Bacteria; Proteobacteria; Teredinibacter Gammaproteobacteria; Yang et al. 2009 GA17030.A.G10 85/41 turnerae CP001614 2.55e-98 Alteromonadales; [52] Total 688/450</p>