[en] Research in 2007 continued the general program of analysing microorganisms and gas in deep groundwater. New tasks examined the presence of anaerobic methane oxidation, the growth of slime on the tunnel walls of ONKALO, and the possible presence of microorganisms that produce complexing agents in groundwater and the slime. Microbiology, chemistry, and dissolved gas data were assembled in 2007 from three deep drillholes in Olkiluoto, Finland, ranging in depth from 39.5 to 294.0 m and in 2005-2007 from six drillholes in ONKALO ranging in depth from 7.1 to 78.5 m. In addition, 24 analyses of gas from nine deep drillholes ranging in depth from 16 to 490 m and one analysis of gas from an ONKALO drillhole of a depth of 14.6 m were executed. The microbiology of shallow and deep groundwater from Olkiluoto had previously been analysed for almost three years from 2004 to 2006. Microbiological and geochemical data strongly suggested that the anaerobic microbial oxidation of methane (ANME) is active at a depth of approximately 300 m in Olkiluoto. However, proof of the presence and activity of ANME microorganisms was deemed necessary before the existence of active ANME processes in Olkiluoto groundwater could be accepted. Part of the research on behalf of Posiva Oy in 2007 therefore was focused on the development and testing of methods for detecting ANME microorganisms. The groundwater from the ONKALO tunnel was also analysed, and slimy biofilms were found growing on the rock walls at some positions in ONKALO late 2006. It was assumed that the ONKALO slime microbes were growing on various substances added to the shotcrete, the injected concrete, or both. Part of the 2007 research focused on detailed analysis of the slime microorganisms and their potential for acid production. The presence of microorganisms that produce complexing agents, for example, siderophores such as pyoverdin and ferrioxamine, was indicated in 2006 in the ONKALO slime as judged from DNA diversity data. It was deemed important to start researching the prevalence of microbes, present in Olkiluoto groundwater and ONKALO slime, having the ability to produce complexing agents. The total amount of gas was found to increase with depth, as was the case in previous years. There was great variability in total gas volume over depth down to a depth of approximately 300 m, consistent with the results from 2005-2006. Three different methods were used to analyse the groundwater samples: TNC returns cell numbers, adenosine triphosphate (ATP) returns a measure of biomass, and cultivation returns a measure of microbe diversity and numbers. The outputs of these independent methods were found to correlate. ATP and TNC have previously been shown to correlate, but the demonstration of correlation between ATP and most probable number (MPN) cultivations is new and supports the quality of the MPN results. Adding a quantitative polymerase chain reaction (Q-PCR) method to groundwater investigations, combined with isolating and characterizing cultivable microorganisms from the highest dilutions of the MPN tubes, will reveal specific details about the diversity and activity of the studied populations. Q-PCR methods were successfully developed in 2007. A schematic model of the processes ongoing in the ONKALO slime has been postulated. Formaldehyde and other organic compounds from the grout additions and the methane promote the growth of methanotrophs and aerobic and iron-reducing microbes in the ONKALO slime. Oxygen can be derived from the air and ferric iron from iron oxides. Methanogens, located deep within the ONKALO slime where oxygen is depleted, produce methane as a final decomposition step after the organic carbon sources added with the grouting are degraded by the aerobic microbes. Sulphide is produced via sulphate reduction and precipitates with ferrous iron forming iron sulphide, which subsequently is converted to sulphuric acid in contact with air, causing pit corrosion of concrete. The results suggest that microbes that produce complexing agents are favoured by the grouting a dditions. Research in 2007 also investigated microorganisms that produce complexing agents in Olkiluoto and ONKALO. Samples were analysed for DNA signatures typical of pyoverdin producers such as Pseudomonadaceae and Shewanella. The results indicate that such microorganisms were more common than expected. They were frequently found in numbers of 1000 or more per mL of groundwater and were also found in the ONKALO slime. Several organisms were isolated and tested for their production of complexing agents, which are produced under both aerobic and anaerobic conditions. Detailed characterization of the isolates is continued in 2008. (orig.)