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 n...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 × 109 and 5 × 1010 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 within the bog ecosystem have been obtained and an important baseline for further studies has been established.展开更多
Radionuclides, like radioiodine（^129I）, may escape deep geological nuclear waste repositories and migrate to the surface ecosystems. In surface ecosystems, microorganisms can affect their movement. Iodide uptake of ...Radionuclides, like radioiodine（^129I）, may escape deep geological nuclear waste repositories and migrate to the surface ecosystems. In surface ecosystems, microorganisms can affect their movement. Iodide uptake of six bacterial strains belonging to the genera Paenibacillus,Pseudomonas, Burkholderia and Rhodococcus isolated from an acidic boreal nutrient-poor bog was tested. The tests were run in four different growth media at three temperatures. All bacterial strains removed iodide from the solution with the highest efficiency shown by one of the Paenibacillus strains with 〉 99% of iodide removed from the solution in one of the used growth media. Pseudomonas, Rhodococcus and one of the two Paenibacillus strains showed highest iodide uptake in 1% yeast extract with maximum values for the distribution coefficient（Kd） ranging from 90 to 270 L/kg DW. The Burkholderia strain showed highest uptake in 1% Tryptone（maximum Kd170 L/kg DW）. The Paenibacillus strain V0-1-LW showed exceptionally high uptake in 0.5% peptone ＋ 0.25% yeast extract broth（maximum Kd〉 1,000,000 L/kg DW）. Addition of 0.1% glucose to the 0.5% peptone ＋ 0.25% yeast extract broth reduced iodide uptake at 4℃ and 20℃ and enhanced iodide uptake at 37℃ compared to the uptake without glucose. This indicates that the uptake of glucose and iodide may be competing processes in these bacteria. We estimated that in in situ conditions of the bog,the bacterial uptake of iodide accounts for approximately 0.1%–0.3% of the total sorption of iodide in the surface, subsurface peat, gyttja and clay layers.展开更多
文摘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 × 109 and 5 × 1010 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 within the bog ecosystem have been obtained and an important baseline for further studies has been established.
基金a part of a research programme funded by Posiva Ltd. concerning safety analysis of final disposal of spent nuclear fuel
文摘Radionuclides, like radioiodine（^129I）, may escape deep geological nuclear waste repositories and migrate to the surface ecosystems. In surface ecosystems, microorganisms can affect their movement. Iodide uptake of six bacterial strains belonging to the genera Paenibacillus,Pseudomonas, Burkholderia and Rhodococcus isolated from an acidic boreal nutrient-poor bog was tested. The tests were run in four different growth media at three temperatures. All bacterial strains removed iodide from the solution with the highest efficiency shown by one of the Paenibacillus strains with 〉 99% of iodide removed from the solution in one of the used growth media. Pseudomonas, Rhodococcus and one of the two Paenibacillus strains showed highest iodide uptake in 1% yeast extract with maximum values for the distribution coefficient（Kd） ranging from 90 to 270 L/kg DW. The Burkholderia strain showed highest uptake in 1% Tryptone（maximum Kd170 L/kg DW）. The Paenibacillus strain V0-1-LW showed exceptionally high uptake in 0.5% peptone ＋ 0.25% yeast extract broth（maximum Kd〉 1,000,000 L/kg DW）. Addition of 0.1% glucose to the 0.5% peptone ＋ 0.25% yeast extract broth reduced iodide uptake at 4℃ and 20℃ and enhanced iodide uptake at 37℃ compared to the uptake without glucose. This indicates that the uptake of glucose and iodide may be competing processes in these bacteria. We estimated that in in situ conditions of the bog,the bacterial uptake of iodide accounts for approximately 0.1%–0.3% of the total sorption of iodide in the surface, subsurface peat, gyttja and clay layers.
