Natural bacterial communities impact the motility of isotopes, such as radionuclides, in the envi... more Natural bacterial communities impact the motility of isotopes, such as radionuclides, in the environment. As a result of post glacial crustal rebound radionuclides may escape the deep geological repository for spent nuclear fuel on Olkiluoto Island, Finland, and reach surface environments. Lastensuo Bog, a 5300-year-old raised bog in southwestern Finland, functions as analogue ecotope for bogs formed in Olkiluoto due to the crustal rebound. A core comprising the depth profile (0 -7 m depth) of the bog including surface Sphagnum moss, peat and bottom clay was obtained using a stainless steel corer. High throughput sequencing was used to characterize the bacterial communities throughout the bog's depth profile. A total of 12,680 bacterial Operational Taxonomic Units (OTUs) (97% sequence similarity) were detected comprising altogether 40 different bacterial phyla. Of these, 13 phyla were present at all depths, accounting for 97% -99% of the whole bacterial community. The bacterial communities differed notably through the bog's depth profile, dividing it into five distinct strata: 1) the Sphagnum moss layer; 2) 0.5 -3.7 m; 3) 3.7 -4.0 m; 4) 5.5 -6.0 m deep peat; 5) the former seabed clay at 6.5 -7.0 m depth. Acidobacteria, α-and γ-Proteobacteria dominated the surface community, but in the peat Acidobacteria contributed with up to 85% of the bacterial community. The estimated bacterial population density ranged between 2 × 10 9 and 5 × 10 10 16S rRNA gene copies g −1 dry-weight peat. This study revealed that Lastensuo Bog had a highly diverse bacterial community. Most of the taxonomic groups belonged to thus far poorly characterized and uncultured bacteria with unknown physiological role. However, new insights into the distribution of bacterial taxa and their putative roles in organic carbon break down with-* Corresponding author.
(135)Cs is among the most important radionuclides in the long-term safety assessments of spent nu... more (135)Cs is among the most important radionuclides in the long-term safety assessments of spent nuclear fuel, due to its long half-life of 2.3 My and large inventory in spent nuclear fuel. Batch sorption experiments were conducted to evaluate the sorption behavior of radiocesium ((134)Cs) in the surface moss, peat, gyttja, and clay layers of 7-m-deep profiles taken from a nutrient-poor boreal bog. The batch distribution coefficient (Kd) values of radiocesium increased as a function of sampling depth. The highest Kd values, with a geometric mean of 3200 L/kg dry weight (DW), were observed in the bottom clay layer and the lowest in the 0.5-1.0 m peat layer (50 L/kg DW). The maximum sorption in all studied layers was observed at a pH between 7 and 9.5. The in situ Kd values of (133)Cs in surface Sphagnum moss, peat and gyttja samples were one order of magnitude higher than the Kd values obtained using the batch method. The highest in situ Kd values (9040 L/kg DW) were recorded for the s...
(79)Se is among the most important long lived radionuclides in spent nuclear fuel and selenite, S... more (79)Se is among the most important long lived radionuclides in spent nuclear fuel and selenite, SeO3(2-), is its typical form in intermediate redox potential. The sorption behaviour of selenite and the bacterial impact on the selenite sorption in a 7-m-deep profile of a nutrient-poor boreal bog was studied using batch sorption experiments. The batch distribution coefficient (Kd) values of selenite decreased as a function of sampling depth and highest Kd values, 6600 L/kg dry weight (DW), were observed in the surface moss and the lowest in the bottom clay at 1700 L/kg DW. The overall maximum sorption was observed at pH between 3 and 4 and the Kd values were significantly higher in unsterilized compared to sterilized samples. The removal of selenite from solution by Pseudomonas sp., Burkholderia sp., Rhodococcus sp. and Paenibacillus sp. strains isolated from the bog was affected by incubation temperature and time. In addition, the incubation of sterilized surface moss, subsurface pea...
Batch sorption experiments were conducted to evaluate the sorption behaviour of iodide and the mi... more Batch sorption experiments were conducted to evaluate the sorption behaviour of iodide and the microbial impact on iodide sorption in the surface moss, subsurface peat, gyttja, and clay layers of a nutrient-poor boreal bog. The batch distribution coefficient (Kd) values of iodide decreased as a function of sampling depth. The highest Kd values, 4800 L/Kg dry weight (DW) (geometric mean), were observed in the fresh surface moss and the lowest in the bottom clay (geometric mean 90 mL/g DW). In the surface moss, peat and gyttja layers, which have a high organic matter content (on average 97%), maximum sorption was observed at a pH between ∼4 and 5 and in the clay layer at pH 2. The Kd values were significantly lower in sterilized samples, being 20-fold lower than the values found for the unsterilized samples. In addition, the recolonization of sterilized samples with a microbial population from the fresh samples restored the sorption capacity of surface moss, peat and gyttja samples, i...
Different types of non-extremophilic archaea have been detected in many different environments, r... more Different types of non-extremophilic archaea have been detected in many different environments, ranging from terrestrial to marine and lacustrine ecosystems. The diversity, function and abundance of most of these, predominantly uncultured archaea is not yet clear. The methanogenic archaea are an exception, but also their functions and spatial and temporal distribution in freshwater environments is not well known. The methanogens have a considerable effect on factors affecting global climate change and many of the novel archaea have only recently been discovered to have influence on global biogeochemical cycles. This review will concentrate on freshwater ecosystems, emphasising the importance of the archaeal communities in freshwater.
Different types of non-extremophilic archaea have been detected in many different environments, r... more Different types of non-extremophilic archaea have been detected in many different environments, ranging from terrestrial to marine and lacustrine ecosystems. The diversity, function and abundance of most of these, predominantly uncultured archaea is not yet clear. The methanogenic archaea are an exception, but also their functions and spatial and temporal distribution in freshwater environments is not well known. The methanogens have a considerable effect on factors affecting global climate change and many of the novel archaea have only recently been discovered to have influence on global biogeochemical cycles. This review will concentrate on freshwater ecosystems, emphasising the importance of the archaeal communities in freshwater.
Active microbial communities of deep crystalline bedrock fracture water were investigated from se... more Active microbial communities of deep crystalline bedrock fracture water were investigated from seven different boreholes in Olkiluoto (Western Finland) using bacterial and archaeal 16S rRNA, dsrB, and mcrA gene transcript targeted 454 pyrosequencing. Over a depth range of 296-798 m below ground surface the microbial communities changed according to depth, salinity gradient, and sulphate and methane concentrations. The highest bacterial diversity was observed in the sulphate-methane mixing zone (SMMZ) at 250-350 m depth, whereas archaeal diversity was highest in the lowest boundaries of the SMMZ. Sulphide-oxidizing ε-proteobacteria (Sulfurimonas sp.) dominated in the SMMZ and γ-proteobacteria (Pseudomonas spp.) below the SMMZ. The active archaeal communities consisted mostly of ANME-2D and Thermoplasmatales groups, although Methermicoccaceae, Methanobacteriaceae, and Thermoplasmatales (SAGMEG, TMG) were more common at 415-559 m depth. Typical indicator microorganisms for sulphate-methane transition zones in marine sediments, such as ANME-1 archaea, α-, β- and δ-proteobacteria, JS1, Actinomycetes, Planctomycetes, Chloroflexi, and MBGB Crenarchaeota were detected at specific depths. DsrB genes were most numerous and most actively transcribed in the SMMZ while the mcrA gene concentration was highest in the deep methane rich groundwater. Our results demonstrate that active and highly diverse but sparse and stratified microbial communities inhabit the Fennoscandian deep bedrock ecosystems.
Low and intermediate level nuclear waste composed mainly of carbon and stainless steel produced d... more Low and intermediate level nuclear waste composed mainly of carbon and stainless steel produced during operation, maintenance and decommissioning of nuclear power plants is disposed of in underground repository, which will be exposed to groundwater. The corrosive effect of groundwater and microbes naturally occurring in groundwater on carbon and stainless steel is assumed to be decreased, when pH of the groundwater has increased due to its contact with the concrete of the repository silos. Nevertheless, after one-year exposure to the repository environment, including the alkaline effect of concrete, the formation of biofilm on the steel surfaces was not completely inhibited, but mainly slowed down. According to weight loss determinations the presence of concrete clearly diminished the corrosion rates of carbon steel at least in the early stages of biofilm formation. No corrosion or biofilm were detected on the surfaces of stainless steel. Our results demonstrate that especially methylotrophic bacteria of the α-proteobacterial clade play a main role in the initial biofilm formation under repository conditions.
The diversity and functional role of fungi, one of the ecologically most important groups of euka... more The diversity and functional role of fungi, one of the ecologically most important groups of eukaryotic microorganisms, remains largely unknown in deep biosphere environments. In this study we investigated fungal communities in packer-isolated bedrock fractures in Olkiluoto, Finland at depths ranging from 296 to 798 m below surface level. DNA-and cDNA-based high-throughput amplicon sequencing analysis of the fungal internal transcribed spacer (ITS) gene markers was used to examine the total fungal diversity and to identify the active members in deep fracture zones at different depths. Results showed that fungi were present in fracture zones at all depths and fungal diversity was higher than expected. Most of the observed fungal sequences belonged to the phylum Ascomycota. Phyla Basidiomycota and Chytridiomycota were only represented as a minor part of the fungal community. Dominating fungal classes in the deep bedrock aquifers were Sordariomycetes, Eurotiomycetes, and Dothideomycetes from the Ascomycota phylum and classes Microbotryomycetes and Tremellomycetes from the Basidiomycota phylum, which are the most frequently detected fungal taxa reported also from deep sea environments. In addition some fungal sequences represented potentially novel fungal species. Active fungi were detected in most of the fracture zones, which proves that fungi are able to maintain cellular activity in these oligotrophic conditions. Possible roles of fungi and their origin in deep bedrock groundwater can only be speculated in the light of current knowledge but some species may be specifically adapted to deep subsurface environment and may play important roles in the utilization and recycling of nutrients and thus sustaining the deep subsurface microbial community.
Archaea belong to the least well known major group of soil inhabiting microbes as the concept of ... more Archaea belong to the least well known major group of soil inhabiting microbes as the concept of the very existence of the archaea was introduced only in 1977 and the domain of Archaea established in 1990. The first reports of finding these organisms in soils were published even later. This paper will review the research carried out of the archaea in dry moderate soil environments. It will particularly consider the specific habitats where the archaea live in soils, as well as their associations with other organisms. There is thus far relatively little knowledge about the metabolism of the soil archaea, but the knowledge about their exact habitats and associations as well as their genetic potential point the way to discovering more about the different soil archaeal functions.
The deep subsurface hosts diverse life, but the mechanisms that sustain this diversity remain elu... more The deep subsurface hosts diverse life, but the mechanisms that sustain this diversity remain elusive. Here, we studied microbial communities involved in carbon cycling in deep, dark biosphere and identified anaerobic microbial energy production mechanisms from groundwater of Fennoscandian crystalline bedrock sampled from a deep drill hole in Outokumpu, Finland, by using molecular biological analyses. Carbon cycling pathways, such as carbon assimilation, methane production and methane consumption, were studied with cbbM, rbcL, acsB, accC, mcrA and pmoA marker genes, respectively. Energy sources, i.e. the terminal electron accepting processes of sulphate-reducing and nitrate-reducing communities, were assessed with detection of marker genes dsrB and narG, respectively. While organic carbon is scarce in deep subsurface, the main carbon source for microbes has been hypothesized to be inorganic carbon dioxide. However, our results demonstrate that carbon assimilation is performed throughout the Outokumpu deep scientific drill hole water column by mainly heterotrophic microorganisms such as Clostridia. The source of carbon for the heterotrophic microbial metabolism is likely the Outokumpu bedrock, mainly composed of serpentinites and metasediments with black schist interlayers. In addition to organotrophic metabolism, nitrate and sulphate are other possible energy sources. Methanogenic and methanotrophic microorganisms are scarce, but our analyses suggest that the Outokumpu deep biosphere provides niches for these organisms; however, they are not very abundant.
Natural bacterial communities impact the motility of isotopes, such as radionuclides, in the envi... more Natural bacterial communities impact the motility of isotopes, such as radionuclides, in the environment. As a result of post glacial crustal rebound radionuclides may escape the deep geological repository for spent nuclear fuel on Olkiluoto Island, Finland, and reach surface environments. Lastensuo Bog, a 5300-year-old raised bog in southwestern Finland, functions as analogue ecotope for bogs formed in Olkiluoto due to the crustal rebound. A core comprising the depth profile (0 -7 m depth) of the bog including surface Sphagnum moss, peat and bottom clay was obtained using a stainless steel corer. High throughput sequencing was used to characterize the bacterial communities throughout the bog's depth profile. A total of 12,680 bacterial Operational Taxonomic Units (OTUs) (97% sequence similarity) were detected comprising altogether 40 different bacterial phyla. Of these, 13 phyla were present at all depths, accounting for 97% -99% of the whole bacterial community. The bacterial communities differed notably through the bog's depth profile, dividing it into five distinct strata: 1) the Sphagnum moss layer; 2) 0.5 -3.7 m; 3) 3.7 -4.0 m; 4) 5.5 -6.0 m deep peat; 5) the former seabed clay at 6.5 -7.0 m depth. Acidobacteria, α-and γ-Proteobacteria dominated the surface community, but in the peat Acidobacteria contributed with up to 85% of the bacterial community. The estimated bacterial population density ranged between 2 × 10 9 and 5 × 10 10 16S rRNA gene copies g −1 dry-weight peat. This study revealed that Lastensuo Bog had a highly diverse bacterial community. Most of the taxonomic groups belonged to thus far poorly characterized and uncultured bacteria with unknown physiological role. However, new insights into the distribution of bacterial taxa and their putative roles in organic carbon break down with-* Corresponding author.
Microorganisms in the deep biosphere are believed to conduct little metabolic activity due to low... more Microorganisms in the deep biosphere are believed to conduct little metabolic activity due to low nutrient availability in these environments. However, destructive penetration to long-isolated bedrock environments during construction of underground waste repositories can lead to increased nutrient availability and potentially affect the long-term stability of the repository systems, Here, we studied how microorganisms present in fracture fluid from a depth of 500 m in Outokumpu, Finland, respond to simple carbon compounds (C-1 compounds) in the presence or absence of sulphate as an electron acceptor. C-1 compounds such as methane and methanol are important intermediates in the deep subsurface carbon cycle, and electron acceptors such as sulphate are critical components of oxidation processes. Fracture fluid samples were incubated in vitro with either methane or methanol in the presence or absence of sulphate as an electron acceptor. Metabolic response was measured by staining the microbial cells with fluorescent dyes that indicate metabolic activity and transcriptional response with RT-qPCR. Our results show that deep subsurface microbes exist in dormant states but rapidly reactivate their transcription and respiration systems in the presence of C-1 substrates, particularly methane. Microbial activity was further enhanced by the addition of sulphate as an electron acceptor. Sulphate-and nitrate-reducing
Natural bacterial communities impact the motility of isotopes, such as radionuclides, in the envi... more Natural bacterial communities impact the motility of isotopes, such as radionuclides, in the environment. As a result of post glacial crustal rebound radionuclides may escape the deep geological repository for spent nuclear fuel on Olkiluoto Island, Finland, and reach surface environments. Lastensuo Bog, a 5300-year-old raised bog in southwestern Finland, functions as analogue ecotope for bogs formed in Olkiluoto due to the crustal rebound. A core comprising the depth profile (0 -7 m depth) of the bog including surface Sphagnum moss, peat and bottom clay was obtained using a stainless steel corer. High throughput sequencing was used to characterize the bacterial communities throughout the bog's depth profile. A total of 12,680 bacterial Operational Taxonomic Units (OTUs) (97% sequence similarity) were detected comprising altogether 40 different bacterial phyla. Of these, 13 phyla were present at all depths, accounting for 97% -99% of the whole bacterial community. The bacterial communities differed notably through the bog's depth profile, dividing it into five distinct strata: 1) the Sphagnum moss layer; 2) 0.5 -3.7 m; 3) 3.7 -4.0 m; 4) 5.5 -6.0 m deep peat; 5) the former seabed clay at 6.5 -7.0 m depth. Acidobacteria, α-and γ-Proteobacteria dominated the surface community, but in the peat Acidobacteria contributed with up to 85% of the bacterial community. The estimated bacterial population density ranged between 2 × 10 9 and 5 × 10 10 16S rRNA gene copies g −1 dry-weight peat. This study revealed that Lastensuo Bog had a highly diverse bacterial community. Most of the taxonomic groups belonged to thus far poorly characterized and uncultured bacteria with unknown physiological role. However, new insights into the distribution of bacterial taxa and their putative roles in organic carbon break down with-* Corresponding author.
(135)Cs is among the most important radionuclides in the long-term safety assessments of spent nu... more (135)Cs is among the most important radionuclides in the long-term safety assessments of spent nuclear fuel, due to its long half-life of 2.3 My and large inventory in spent nuclear fuel. Batch sorption experiments were conducted to evaluate the sorption behavior of radiocesium ((134)Cs) in the surface moss, peat, gyttja, and clay layers of 7-m-deep profiles taken from a nutrient-poor boreal bog. The batch distribution coefficient (Kd) values of radiocesium increased as a function of sampling depth. The highest Kd values, with a geometric mean of 3200 L/kg dry weight (DW), were observed in the bottom clay layer and the lowest in the 0.5-1.0 m peat layer (50 L/kg DW). The maximum sorption in all studied layers was observed at a pH between 7 and 9.5. The in situ Kd values of (133)Cs in surface Sphagnum moss, peat and gyttja samples were one order of magnitude higher than the Kd values obtained using the batch method. The highest in situ Kd values (9040 L/kg DW) were recorded for the s...
(79)Se is among the most important long lived radionuclides in spent nuclear fuel and selenite, S... more (79)Se is among the most important long lived radionuclides in spent nuclear fuel and selenite, SeO3(2-), is its typical form in intermediate redox potential. The sorption behaviour of selenite and the bacterial impact on the selenite sorption in a 7-m-deep profile of a nutrient-poor boreal bog was studied using batch sorption experiments. The batch distribution coefficient (Kd) values of selenite decreased as a function of sampling depth and highest Kd values, 6600 L/kg dry weight (DW), were observed in the surface moss and the lowest in the bottom clay at 1700 L/kg DW. The overall maximum sorption was observed at pH between 3 and 4 and the Kd values were significantly higher in unsterilized compared to sterilized samples. The removal of selenite from solution by Pseudomonas sp., Burkholderia sp., Rhodococcus sp. and Paenibacillus sp. strains isolated from the bog was affected by incubation temperature and time. In addition, the incubation of sterilized surface moss, subsurface pea...
Batch sorption experiments were conducted to evaluate the sorption behaviour of iodide and the mi... more Batch sorption experiments were conducted to evaluate the sorption behaviour of iodide and the microbial impact on iodide sorption in the surface moss, subsurface peat, gyttja, and clay layers of a nutrient-poor boreal bog. The batch distribution coefficient (Kd) values of iodide decreased as a function of sampling depth. The highest Kd values, 4800 L/Kg dry weight (DW) (geometric mean), were observed in the fresh surface moss and the lowest in the bottom clay (geometric mean 90 mL/g DW). In the surface moss, peat and gyttja layers, which have a high organic matter content (on average 97%), maximum sorption was observed at a pH between ∼4 and 5 and in the clay layer at pH 2. The Kd values were significantly lower in sterilized samples, being 20-fold lower than the values found for the unsterilized samples. In addition, the recolonization of sterilized samples with a microbial population from the fresh samples restored the sorption capacity of surface moss, peat and gyttja samples, i...
Different types of non-extremophilic archaea have been detected in many different environments, r... more Different types of non-extremophilic archaea have been detected in many different environments, ranging from terrestrial to marine and lacustrine ecosystems. The diversity, function and abundance of most of these, predominantly uncultured archaea is not yet clear. The methanogenic archaea are an exception, but also their functions and spatial and temporal distribution in freshwater environments is not well known. The methanogens have a considerable effect on factors affecting global climate change and many of the novel archaea have only recently been discovered to have influence on global biogeochemical cycles. This review will concentrate on freshwater ecosystems, emphasising the importance of the archaeal communities in freshwater.
Different types of non-extremophilic archaea have been detected in many different environments, r... more Different types of non-extremophilic archaea have been detected in many different environments, ranging from terrestrial to marine and lacustrine ecosystems. The diversity, function and abundance of most of these, predominantly uncultured archaea is not yet clear. The methanogenic archaea are an exception, but also their functions and spatial and temporal distribution in freshwater environments is not well known. The methanogens have a considerable effect on factors affecting global climate change and many of the novel archaea have only recently been discovered to have influence on global biogeochemical cycles. This review will concentrate on freshwater ecosystems, emphasising the importance of the archaeal communities in freshwater.
Active microbial communities of deep crystalline bedrock fracture water were investigated from se... more Active microbial communities of deep crystalline bedrock fracture water were investigated from seven different boreholes in Olkiluoto (Western Finland) using bacterial and archaeal 16S rRNA, dsrB, and mcrA gene transcript targeted 454 pyrosequencing. Over a depth range of 296-798 m below ground surface the microbial communities changed according to depth, salinity gradient, and sulphate and methane concentrations. The highest bacterial diversity was observed in the sulphate-methane mixing zone (SMMZ) at 250-350 m depth, whereas archaeal diversity was highest in the lowest boundaries of the SMMZ. Sulphide-oxidizing ε-proteobacteria (Sulfurimonas sp.) dominated in the SMMZ and γ-proteobacteria (Pseudomonas spp.) below the SMMZ. The active archaeal communities consisted mostly of ANME-2D and Thermoplasmatales groups, although Methermicoccaceae, Methanobacteriaceae, and Thermoplasmatales (SAGMEG, TMG) were more common at 415-559 m depth. Typical indicator microorganisms for sulphate-methane transition zones in marine sediments, such as ANME-1 archaea, α-, β- and δ-proteobacteria, JS1, Actinomycetes, Planctomycetes, Chloroflexi, and MBGB Crenarchaeota were detected at specific depths. DsrB genes were most numerous and most actively transcribed in the SMMZ while the mcrA gene concentration was highest in the deep methane rich groundwater. Our results demonstrate that active and highly diverse but sparse and stratified microbial communities inhabit the Fennoscandian deep bedrock ecosystems.
Low and intermediate level nuclear waste composed mainly of carbon and stainless steel produced d... more Low and intermediate level nuclear waste composed mainly of carbon and stainless steel produced during operation, maintenance and decommissioning of nuclear power plants is disposed of in underground repository, which will be exposed to groundwater. The corrosive effect of groundwater and microbes naturally occurring in groundwater on carbon and stainless steel is assumed to be decreased, when pH of the groundwater has increased due to its contact with the concrete of the repository silos. Nevertheless, after one-year exposure to the repository environment, including the alkaline effect of concrete, the formation of biofilm on the steel surfaces was not completely inhibited, but mainly slowed down. According to weight loss determinations the presence of concrete clearly diminished the corrosion rates of carbon steel at least in the early stages of biofilm formation. No corrosion or biofilm were detected on the surfaces of stainless steel. Our results demonstrate that especially methylotrophic bacteria of the α-proteobacterial clade play a main role in the initial biofilm formation under repository conditions.
The diversity and functional role of fungi, one of the ecologically most important groups of euka... more The diversity and functional role of fungi, one of the ecologically most important groups of eukaryotic microorganisms, remains largely unknown in deep biosphere environments. In this study we investigated fungal communities in packer-isolated bedrock fractures in Olkiluoto, Finland at depths ranging from 296 to 798 m below surface level. DNA-and cDNA-based high-throughput amplicon sequencing analysis of the fungal internal transcribed spacer (ITS) gene markers was used to examine the total fungal diversity and to identify the active members in deep fracture zones at different depths. Results showed that fungi were present in fracture zones at all depths and fungal diversity was higher than expected. Most of the observed fungal sequences belonged to the phylum Ascomycota. Phyla Basidiomycota and Chytridiomycota were only represented as a minor part of the fungal community. Dominating fungal classes in the deep bedrock aquifers were Sordariomycetes, Eurotiomycetes, and Dothideomycetes from the Ascomycota phylum and classes Microbotryomycetes and Tremellomycetes from the Basidiomycota phylum, which are the most frequently detected fungal taxa reported also from deep sea environments. In addition some fungal sequences represented potentially novel fungal species. Active fungi were detected in most of the fracture zones, which proves that fungi are able to maintain cellular activity in these oligotrophic conditions. Possible roles of fungi and their origin in deep bedrock groundwater can only be speculated in the light of current knowledge but some species may be specifically adapted to deep subsurface environment and may play important roles in the utilization and recycling of nutrients and thus sustaining the deep subsurface microbial community.
Archaea belong to the least well known major group of soil inhabiting microbes as the concept of ... more Archaea belong to the least well known major group of soil inhabiting microbes as the concept of the very existence of the archaea was introduced only in 1977 and the domain of Archaea established in 1990. The first reports of finding these organisms in soils were published even later. This paper will review the research carried out of the archaea in dry moderate soil environments. It will particularly consider the specific habitats where the archaea live in soils, as well as their associations with other organisms. There is thus far relatively little knowledge about the metabolism of the soil archaea, but the knowledge about their exact habitats and associations as well as their genetic potential point the way to discovering more about the different soil archaeal functions.
The deep subsurface hosts diverse life, but the mechanisms that sustain this diversity remain elu... more The deep subsurface hosts diverse life, but the mechanisms that sustain this diversity remain elusive. Here, we studied microbial communities involved in carbon cycling in deep, dark biosphere and identified anaerobic microbial energy production mechanisms from groundwater of Fennoscandian crystalline bedrock sampled from a deep drill hole in Outokumpu, Finland, by using molecular biological analyses. Carbon cycling pathways, such as carbon assimilation, methane production and methane consumption, were studied with cbbM, rbcL, acsB, accC, mcrA and pmoA marker genes, respectively. Energy sources, i.e. the terminal electron accepting processes of sulphate-reducing and nitrate-reducing communities, were assessed with detection of marker genes dsrB and narG, respectively. While organic carbon is scarce in deep subsurface, the main carbon source for microbes has been hypothesized to be inorganic carbon dioxide. However, our results demonstrate that carbon assimilation is performed throughout the Outokumpu deep scientific drill hole water column by mainly heterotrophic microorganisms such as Clostridia. The source of carbon for the heterotrophic microbial metabolism is likely the Outokumpu bedrock, mainly composed of serpentinites and metasediments with black schist interlayers. In addition to organotrophic metabolism, nitrate and sulphate are other possible energy sources. Methanogenic and methanotrophic microorganisms are scarce, but our analyses suggest that the Outokumpu deep biosphere provides niches for these organisms; however, they are not very abundant.
Natural bacterial communities impact the motility of isotopes, such as radionuclides, in the envi... more Natural bacterial communities impact the motility of isotopes, such as radionuclides, in the environment. As a result of post glacial crustal rebound radionuclides may escape the deep geological repository for spent nuclear fuel on Olkiluoto Island, Finland, and reach surface environments. Lastensuo Bog, a 5300-year-old raised bog in southwestern Finland, functions as analogue ecotope for bogs formed in Olkiluoto due to the crustal rebound. A core comprising the depth profile (0 -7 m depth) of the bog including surface Sphagnum moss, peat and bottom clay was obtained using a stainless steel corer. High throughput sequencing was used to characterize the bacterial communities throughout the bog's depth profile. A total of 12,680 bacterial Operational Taxonomic Units (OTUs) (97% sequence similarity) were detected comprising altogether 40 different bacterial phyla. Of these, 13 phyla were present at all depths, accounting for 97% -99% of the whole bacterial community. The bacterial communities differed notably through the bog's depth profile, dividing it into five distinct strata: 1) the Sphagnum moss layer; 2) 0.5 -3.7 m; 3) 3.7 -4.0 m; 4) 5.5 -6.0 m deep peat; 5) the former seabed clay at 6.5 -7.0 m depth. Acidobacteria, α-and γ-Proteobacteria dominated the surface community, but in the peat Acidobacteria contributed with up to 85% of the bacterial community. The estimated bacterial population density ranged between 2 × 10 9 and 5 × 10 10 16S rRNA gene copies g −1 dry-weight peat. This study revealed that Lastensuo Bog had a highly diverse bacterial community. Most of the taxonomic groups belonged to thus far poorly characterized and uncultured bacteria with unknown physiological role. However, new insights into the distribution of bacterial taxa and their putative roles in organic carbon break down with-* Corresponding author.
Microorganisms in the deep biosphere are believed to conduct little metabolic activity due to low... more Microorganisms in the deep biosphere are believed to conduct little metabolic activity due to low nutrient availability in these environments. However, destructive penetration to long-isolated bedrock environments during construction of underground waste repositories can lead to increased nutrient availability and potentially affect the long-term stability of the repository systems, Here, we studied how microorganisms present in fracture fluid from a depth of 500 m in Outokumpu, Finland, respond to simple carbon compounds (C-1 compounds) in the presence or absence of sulphate as an electron acceptor. C-1 compounds such as methane and methanol are important intermediates in the deep subsurface carbon cycle, and electron acceptors such as sulphate are critical components of oxidation processes. Fracture fluid samples were incubated in vitro with either methane or methanol in the presence or absence of sulphate as an electron acceptor. Metabolic response was measured by staining the microbial cells with fluorescent dyes that indicate metabolic activity and transcriptional response with RT-qPCR. Our results show that deep subsurface microbes exist in dormant states but rapidly reactivate their transcription and respiration systems in the presence of C-1 substrates, particularly methane. Microbial activity was further enhanced by the addition of sulphate as an electron acceptor. Sulphate-and nitrate-reducing
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Papers by Malin Bomberg