MDS graphs were plotted using a non-metric configuration in which the distance between any two points is inversely proportional to their similarity. All MDS analyses were performed using the Primer-6 software package (Primer-E Ltd., Plymouth, UK). The overall similarity of the bacterial and archaeal

communities within groups of wells was calculated using the analysis of similarity (ANOSIM) [38]. Specifically, R-values (RANOSIM) learn more were used to establish the dissimilarity of different paired-groups of microbial communities (e.g. communities from no sulfate vs. high sulfate groundwater). RANOSIM > 0.75 HKI-272 manufacturer indicate two microbial communities (i.e. the attached and suspended communities from PCI-34051 in vivo various wells in an aquifer) have characteristic structures largely distinct from one another [39]. A value of RANOSIM between

0.25 and 0.75 indicates communities within each group cluster separately from those in the other, with some overlap, while an RANOSIM < 0.25 indicates communities in one group are almost indistinguishable from those in the other. SIMPER (similarity percentage) was used to calculate the extent to which individual OTUs contribute to the dissimilarity groups sets and to rank the populations from most to least responsible for the differences between groups [40, 41]. Representative sequences from each OTU were identified using Mothur and identified using the Greengenes reference taxonomy as described above. Representative sequences were deposited in GenBank under accession numbers KC604413 to KC604575 and KC604576 to KC607489. Results Groundwater geochemistry Table

1 shows that the concentrations of sulfate (SO4 2–), methane (CH4), and dihydrogen Montelukast Sodium (H2) in groundwater from the Mahomet wells each varied over several orders of magnitude (Table 1). The concentration of sulfate ranged from 10.7 mM to below the detection limit of 0.01 mM. We used the sulfate concentration in groundwater samples to classify each well following the scheme devised by Panno et al.[17] for the Mahomet aquifer. We designated nine wells as high sulfate (HS; [SO4 2-] > 0.2 mM), eight as low sulfate (LS; [SO4 2-] = 0.03 – 0.2 mM), and eight wells as negligible sulfate (NS, [SO4 2-] < 0.03 mM). While methane was not considered in Panno et al. classification, we found an inverse relationship exists between the concentration of dissolved methane and that of sulfate (Figure 2). Dissolved methane ranged from below detection (< 0.2 μM) to 1240 μM, with the highest concentrations occurring in NS wells ([CH4 (aq)] = 220–1240 μM). Dissolved methane was not detected in three of the eight HS wells, and concentrations were < 3 μM in four of the others. The concentration of dissolved H2, however, ranged from 3 to 240 nM and did not correlate to any other measured geochemical species. Table 1 Geochemistry of groundwater in Mahomet aquifer wells Well Temp. (°C) pH sp. Cond.