(San Bruno, CA, USA) as Title Loaded From File outlined in Supplementary components and procedures.Statistical analysesData graphics style and statistical Title Loaded From File analyses have been performed in Statistica 10 (Statsoft Inc., Tulsa, OK, USA).ResultsExperimental conditionsPrevious groundwater microbiology experiments at in situ pressure and chemistry have been performed from start off to finish inside the underground Aspo HRL (Nielsen et al., 2006; Anderson et al., 2007; Pedersen, 2012a, b). In the present function, the transfer from the pressurized FCs, containing biofilms and groundwater, to the FCCs in the ground-level laboratory supplied improved continuous surveillance with the systems and much more efficient sampling and analytical conditions than within the prior underground FCC installation.Groundwater characterizationTotal number of cells 37 000 -- 6100 ATP 27 300 3170 Cultivable hetero16 300 -- 3210 trophic aerobic bacteria Nitrate-reducing 90 000 -- -- bacteria Iron-reducing bacteria 500 -- -- Manganese-reducing 220 -- -- bacteria Sulphate-reducing 80 -- -- bacteria Autotrophic acetogens 17 -- -- Heterotrophic 110 -- -- acetogens Autotrophic o0.2 -- -- methanogens Heterotrophic o0.two -- -- methanogensThere were 3.7 104 cells ml and 2.8 104 amol ATP ml within the groundwater analysed on 23 September 2010. NRB dominated the MPN determination and, except for the MPN of methanogens, all samples have been above the detection limit (Table 1). The groundwater analysed on eight November 2010 had a pH of 7.six (analysed inside the Teollisuuden Voima Oy laboratory), a conductivity of 1520 ms m, plus a temperature of 11 1C. The important dissolved solids were 150 mM Cl 91 mM Na , 28 mM Ca2 and 1.0 mM SO2 The following had been 4 also analysed: POand NOat o0.01 mM, 1.7 mM 4 3 NH4 , 36 mM Fe2 , o0.01 mM HS 230 mM HCO3 and 0.two mM DOC. There was 0.07 mM H2 and 4.five mM CH4 dissolved within the groundwater analysed on 23 September 2010.pH, Eh and gasesThe pH enhanced in the beginning value of roughly 7.4 to about eight.5 within the H2:CH4 FCC after 40 days, but didn‘t raise within the other two FCCs (Figure 1a). The Eh with the H2:CH4 FCC rapidly decreased to approximately 00 mV, as registered by the internal microelectrodes (Figure 1b). The Eh of the CH4 FCC decreased too, reaching a steady degree of 00 mV soon after 35 days, whereas the Eh on the O2:N2 FCC gradually decreased to 0 mV by the end from the experiment. A technical difficulty occurred together with the electrodes inThe ISME JournalO2:N2, which lost get in touch with with the FCC among days 90 and 110. Sampling the rock grains for ATP and DNA evaluation inevitably introduced modest amounts of O2 when the FCs had been opened, as indicated by the peaks in Eh just after every sampling occasion (Figure 1b). This effect diminished inside some days, as expected from preceding Aspo HRL final results, indicating the effect of adding 0.1.two mM O2 (Pedersen, 2012b). The internal Eh electrodes reported these effects in continuous mode and have been superior in sensitivity towards the external Eh electrode (Figure 1c). The addition of gases resulted in anticipated concentrations of H2 (10 mM) and methane (11 mM; Figures 1d and e). The O2 concentration was 2.two mM in the O2:N2 method on day 0 and decreased linearly to 0.two mM by day 105. The H2 conc.