Аннотация:Studies of properties of nanomaterials, which are obtained as a result of microbial synthesis is one of the most important problem of modern physics. The catalyst is necessary for different chemical reactions. On the other hand, the microbial synthesis may be carried out in conditions that are close to natural one. The products of such type synthesis can be the nanoparticles of iron oxides. The reaction leads in organic non-toxic medium, as a result the obtained nanoparticles have the organic shell. These nanoparticles can be used as carrier for target drug delivery. Moreover, these particles can be used for heavy ions removing from soils and water due to the strong chemical activity. The dissimilatory bacterium oxidizes acetate and transports the electron on the surface of ironcontaining
mineral. In this case, the charge of iron atom changes from 3+ to 2+. The electron
concentration on the particles surface depends on the bacterial cells quantity, which influence on it. Therefore, the iron reduction process strongly depends on the ratio between quantities of bacterial cells and particles of minerals. The samples were obtained as a result of iron reduction of ferrihydrite (the concentrations were nFe(III) = 10; 45; 100 мМ) by bacterium Geoalkalibacter ferrihydriticus (strain Z-0531). In the experiment different ratios between quantities of cells and particles of minerals were realized by
different flask orientation. Samples were studied by Mӧssbauer spectroscopy and XRD methods.
The Mӧssbauer spectra of superparamagnetic particles were fitted with many state relaxation model by program SpectrRelax. Mӧssbauer and X-ray measurements showed that the change in the number of cells per particle lead to a change in the size of the formed particles, as well as changes of the ratio between the siderite and magnetite content in the samples.