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Not only since Chernobyl and Fukushima is it well known that fungi can accumulate large amounts of heavy metals and radionuclides. Although there are many publications describing this phenomenon and naming transfer factors, almost nothing is known about the underlying molecular processes being responsible for the binding, uptake and accumulation in the cell or even transport inside the organism for elements like uranium, americium and other heavy radio-metals. However, knowing this is crucial if one wants to understand the influence of fungi on the migration behavior of radionuclides in the environment. It is all the more important to know the underlying biochemical processes and to know how environmental influences affect the radionuclide-cell interaction, if one considers using these extraordinary properties to biologically immobilize radionuclides in contaminated soil or even to remove radionuclides from it. As part of the BioVeStRa project, various fungi have been studied to determine their potential for precautionary radiation protection and the remediation of contaminated soils. Therefore, two fungi were selected based on published transfer factor and a known rapid growth on complex media, namely Schizophyllum commune and Leucoagaricus naucinus. Additionally, two further fungi metabolically related to S. commune or L. naucinus were included also in the studies to determine if similar fungi behave similarly or not. To study the fungi, a combination of growth and binding experiments, mass spectrometry, fluorescence spectroscopy and electron microscopy was used. In summary, it can be stated, that S. commune is not only the most robust fungus that prevails even in the test field against autochthonic soil microbes and fungi, but also shows the highest accumulation rates for uranium and europium, the latter as a substitute for trivalent actinides such as americium. Furthermore, it could be shown that fungi behave very differently depending on the investigated elemen

The varied use of different radionuclides in medicine, industry and research and their disposal has repeat-edly led to the release of these radionuclides into the environment. Through leaching and migration, the anthropogenic released radionuclides can reach the groundwater, endangering the environment, animals and humans. However, the mobility and thus the migration behavior of radionuclides in the soil are influ-enced by the microorganisms living there. Fungi play an important role in the microbial community of soil and can therefore have a major influence on radionuclide mobility, for example through sorption, accumulation or reduction processes. Therefore, the aim of this research is to investigate the influence of fungi on radionuclide migration in soil by using column and field experiments and to determine the potential of fungi for radiation protection precaution-ary methods or even remediation methods. For the assessment of the suitability of fungi the first step is to investigate the molecular interactions with radionuclides under laboratory conditions to identify dominant interaction processes. Therefore binding experiments with different media were performed and the molecular binding form was investigated with time-resolved laser-induced fluorescence spectroscopy. In the next step, column experiments were carried out with soil and under natural conditions, in which the retention capacity of the fungi for radionuclide migration in the soil was investigated. The experiments so far showed that the biochemistry of the fungi determines the metal interaction and not the surrounding environment. Furthermore, it was clearly demonstrated by column experiments, that fungi are able to retain radionuclides significantly.

The varied use of different radionuclides in medicine, industry and research and their disposal has repeat-edly led to the release of these radionuclides into the environment. Through leaching and migration, the anthropogenic released radionuclides can reach the groundwater, endangering the environment, animals and humans. However, the mobility and thus the migration behavior of radionuclides in the soil are influ-enced by the microorganisms living there. Fungi play an important role in the microbial community of soil and can therefore have a major influence on radionuclide mobility, for example through sorption, accumulation or reduction processes. Therefore, the aim of this research is to investigate the influence of fungi on radionuclide migration in soil by using column and field experiments and to determine the potential of fungi for radiation protection precaution-ary methods or even remediation methods. For the assessment of the suitability of fungi the first step is to investigate the molecular interactions with radionuclides under laboratory conditions to identify dominant interaction processes. Therefore binding experiments with different media were performed and the molecular binding form was investigated with time-resolved laser-induced fluorescence spectroscopy. In the next step, column experiments were carried out with soil and under natural conditions, in which the retention capacity of the fungi for radionuclide migration in the soil was investigated. The experiments so far showed that the biochemistry of the fungi determines the metal interaction and not the surrounding environment. Furthermore, it was clearly demonstrated by column experiments, that fungi are able to retain radionuclides significantly.

A direct microscopic method based on the response of bacterial cells to inhibition of DNA synthesis by nalidixic acid in the presence of growth-supporting yeast extract and designed to determine the number of viable bacteria, was tested in marine sediments bioturbated by the deposit-feeding polychaete Arenicola marina. The number of responsive cells in sediment samples ingested and egested by the polychaete, reflected similar differences and trends as total direct counts or plate counts. Nevertheless, application of that viable direct count technique in marine sediments suffered also from considerable systematic errors.

Deposit-feeding benthic macrofauna withdraw substantial amounts of bacterial biomass from marine sediments. On the other hand, burrowing macro-invertebrates can mediate epizoic and perizoic enrichment of bacteria by tapping or "conditioning" energy carriers (for heterotrophic and chemolithotrophic bacteria) that are stored in the sediment. Selected examples show how this applies particularly to reduced sediments.

A direct microscopic method based on the response of bacterial cells to inhibition of DNA synthesis by nalidixic acid in the presence of growth-supporting yeast extract and designed to determine the number of viable bacteria, was tested in marine sediments bioturbated by the deposit-feeding polychaete Arenicola marina. The number of responsive cells in sediment samples ingested and egested by the polychaete, reflected similar differences and trends as total direct counts or plate counts. Nevertheless, application of that viable direct count technique in marine sediments suffered also from considerable systematic errors.

Deposit-feeding benthic macrofauna withdraw substantial amounts of bacterial biomass from marine sediments. On the other hand, burrowing macro-invertebrates can mediate epizoic and perizoic enrichment of bacteria by tapping or "conditioning" energy carriers (for heterotrophic and chemolithotrophic bacteria) that are stored in the sediment. Selected examples show how this applies particularly to reduced sediments.

A direct microscopic method based on the response of bacterial cells to inhibition of DNA synthesis by nalidixic acid in the presence of growth-supporting yeast extract and designed to determine the number of viable bacteria, was tested in marine sediments bioturbated by the deposit-feeding polychaete Arenicola marina. The number of responsive cells in sediment samples ingested and egested by the polychaete, reflected similar differences and trends as total direct counts or plate counts. Nevertheless, application of that viable direct count technique in marine sediments suffered also from considerable systematic errors.

Deposit-feeding benthic macrofauna withdraw substantial amounts of bacterial biomass from marine sediments. On the other hand, burrowing macro-invertebrates can mediate epizoic and perizoic enrichment of bacteria by tapping or "conditioning" energy carriers (for heterotrophic and chemolithotrophic bacteria) that are stored in the sediment. Selected examples show how this applies particularly to reduced sediments.

A direct microscopic method based on the response of bacterial cells to inhibition of DNA synthesis by nalidixic acid in the presence of growth-supporting yeast extract and designed to determine the number of viable bacteria, was tested in marine sediments bioturbated by the deposit-feeding polychaete Arenicola marina. The number of responsive cells in sediment samples ingested and egested by the polychaete, reflected similar differences and trends as total direct counts or plate counts. Nevertheless, application of that viable direct count technique in marine sediments suffered also from considerable systematic errors.

Deposit-feeding benthic macrofauna withdraw substantial amounts of bacterial biomass from marine sediments. On the other hand, burrowing macro-invertebrates can mediate epizoic and perizoic enrichment of bacteria by tapping or "conditioning" energy carriers (for heterotrophic and chemolithotrophic bacteria) that are stored in the sediment. Selected examples show how this applies particularly to reduced sediments.

von S. L. Grossmann

von S. L. Grossmann

von S. L. Grossmann