Changes in 137Cs bioavailability under the influence of soil microflora

Despite the rising safety standards applicable to the nuclear industry enterprises still occur the huge radiation accidents, the consequences of which are large-scale releases of radionuclides into the environment. The soil is the main depot for radioactive substances in the ecosystem and triggering element for their transition through trophic chains up to the human being. That is why the search for new effective methods of soil decontamination, particularly the soil that is used for agriculture, still remains of a big relevance. Using the properties of microorganisms to affect the availability of mineral compounds in the soil may become one of such methods. 137Cs is one of the main dose-forming radionuclides, introduced into the ecosystem as a result of the nuclear weapons testing and accidents occurring at nuclear power plants. Thus, radionuclide contamination of agricultural land and food is a major problem for the exclusion zones, formed after the accidents at the Fukushima Daiichi and the Chernobyl NPPs. To study the role of soil microorganisms in the migration of 137Cs 5 isolates from Chernobyl exclusion zone were allocated and identified in accordance with 16s RNA: Burkholderia glathei Hg11, Burkholderia sp IMER-B1-53, Bacillus mycides BCHMAC12, Flavobacterium sp TISTR 1602, Pseudomonas frederiksbergensis TPK 2-4 and compared their ability to accumulate radionuclide with collection species, which are used as a bio-agents of microbial fertilizers: Bacillusmegaterium UKM B-5724, Azotobacterchroococcum UKM B-6003-20A, Azotobacterchroococcum UKM B-6003-9T, Agrobacterium radiobacter by transfer of isolates to liquid nutrient medium containing 5 kBq 137Cs. It was found that the strain Bacillusmegaterium UKM B-5724 from the collection of the Institute of Microbiology and Virology of NASU, has a high ability to accumulate radionuclides. Figured out that certain types of microorganisms can either reduce or increase the ratio of 137Cs transfer from the substrate to the plant (Brassica napus L.). It is shown that this property is independent of the localization of the microorganism on the surface of the root, for all analyzed bacteria belongs to the rhizospheric group. Azotobacterchroococcum UKM B-6003-20A stimulated the radionuclide transfer to plants up to 1.5 times, while the best bacteria for reducing its accumulation is Burkholderia sp IMER-B1-53- 1.3 times in comparison with the control. (authors)