8% to 89.2% related to Methanomassiliicoccus luminyensis, whereas 33 sequences (44 clones) were 95.5% to 99.1% related

to methanogens belonging to the order Methanobacteriales and six sequences (20 clones) were 99.4 to 99.8% related to those belonging to the order Methanomicrobiales. The remaining two sequences (12 clones) were 92.5% and 92.8% related to Methanimicrococcus blatticola within the order Methanosarcinales. Within the Methanobacteriales, 27 of the 33 sequences were 96.0% to 99.1% identical to Methanobrevibacter millerae, two sequences (QTPC 9 and QTPC 15) were 97.6 to 98.4% related to Methanobrevibacter gottschalkii; one sequence (QTPC 70) was only 95.5% related to Methanobrevibacter arboriphilus; and three sequences (QTPC 112, QTPC 27 and QTPC 110) were 99%. 96.8%

and 95.7% related to Methanobrevibacter ruminantium, Methanobrevibacter smithii and Methanobrevibacter wolinii, respectively. PSI-7977 concentration Using a species-level identity criterion of 98% [13], 93 of the 95 OTUs had less than 98% identity to any valid recognized taxa, and may represent potential new methanogen Belnacasan molecular weight species and strains. Statistical analysis of libraries The yak library had a Shannon index of 3.33±0.18 while the cattle library had a Shannon index of 3.02±0.19. Libshuff analysis showed that the differences between the yak and cattle libraries at 98% identity were significant (P< 0.0001). Phylogenetic placement of sequences Distance-matrix phylogenetic trees are provided showing either the phylogenetic placement of the methanogen sequences from the yak and cattle (Figure 1) clone libraries. Methanogen sequences from yak and cattle grouped with methanogens from the uncharacterized TALC group (Figure 1b), as well as the orders Methanobacteriales, Methanomicrobiales, Methanosarcinales

(Figure 1a). Figure 1 Phylogenetic analysis of methanogen partial 16S rRNA sequences from yak and cattle clone library inferred using MEGA (ver. 5). Of the 414 clones examined, 209 clones from yak and 205 clones from cattle were assigned to 95 OTUs by MOTHUR using a 98% species level identity. These 95 OTUs are shown by representative sequences on the tree. In which, 16 OTUs from non-TALC group are presented in Figure 1a, and 79 OTUs from TALC group are presented in Figure 1b. GenBank accession number are indicated in parentheses and bootstrap values (>50%) from 1000 replications are indicated on the tree.The scale bar corresponds to 2 changes per 100 positions. In total, 414 clones were analyzed, revealing 247 unique sequences (134 sequences from yak and 113 sequences from cattle), which were assigned to 95 OTUs (79 TALC and 16 non-TALC). Examination of these 95 OTUs revealed that, 46 OTUs were unique to the yak clone library and 34 OTUs were unique to the cattle clone library (Figure 1a and 1b), while 15 OTUs (15.8%) were found in both libraries as shared OTUs. Discussion The Yak is a key species in the Qinghai Tibetan Plateau.