FIG 2.

Maximum likelihood phylogenetic tree based on partial arrA gene sequences (∼330 bp) from five soil samples and four groundwater samples from the Cache Valley Basin, amplified with the newly developed PCR primers and sequenced using high-throughput sequencing. Sequences belonging to the same OTU (at 90% identity), as assigned by mothur, were clustered together, and branches within clusters were collapsed to show the overall relationships of these clusters to one another. The major grouping (groups I to V) is consistent with the phylogenetic tree shown in Fig. 1, and three clusters (highlighted in gray) are unique. Numbers at the nodes reflect the maximum likelihood bootstrap support values. A total of 82 OTUs containing more than 100 arrA gene sequences from soil and groundwater samples were used in this analysis. The distributions of arrA gene sequences among the soil and groundwater samples are represented in diamonds and squares, respectively. Numbers at the right correspond to the overall distribution of arrA gene sequences in the major groups and their relative distribution in sediment and groundwater samples. The psrA gene from Wolinella succinogenes (GenBank accession no. X65042) was used as an outgroup.