Yu. L. Gurevich

Mössbauer study of bacterial ferrihydrite

Mössbauer measurements reveal four inequivalent Fe sites in ferrihydrite produced by Klebsiella oxytoca. The origin of these sites can be understood in terms of two nanosized structural regions in the bacterium and a certain ordering of bilayers and single layers of Fe-occupied octahedra.

Iron-containing nanoparticles from microbial metabolism

We have studied the crystal structure and magnetic properties of Fe-containing nanoparticles formed as a result of microbial metabolism. Our experimental data, coupled with earlier results, suggest that the nanoparticles consist of ferrihydrite, Fe2O3 · nH2O, and are in a superparamagnetic state.

Bacterial leaching of manganese ores

Leaching of various types of ores, containing 12–30% manganese, by the thiobacterium Acidithiobacillus ferrooxidans was studied. Leaching of reduced ores (manganocalcite and manganiferous limestone) was mediated mainly by degradation of manganiferous minerals (by sulfuric acid produced in the course of bacterial oxidation of pyrite or sulfur). Bacterial treatment of the ores for 144 and 192 h allowed solubilization of 96–98% of manganese. Inoculation of bacteria into pulp with pyrite increased the rate of leaching of oxide ore (psilomelane) by 37%, and the degree of its extraction within 180 h increased from 80 to 97%.

Mössbauer investigation of iron-producing bacteria Klebsiella oxytoca

The process of ferrihydrite formation in bacteria Klebsiella oxytoca has been investigated as a function of the bacteria cultivation time. The effect of temperature on the ferrihydrite transformations has been studied.

Colony Structure of a Consortium of Nitrifying Bacteria

Colonies produced by a consortium of nitrifying bacteria were studied using light and electron microscopy. The colonies were obtained by direct plating of inoculum from a two-stage nonsterile chemostat fermentor and by repeatedly passing the microbial community of the fermentor through selective media containing ammonium or nitrite. The colonies studied can be characterized by a specific combination of six types of cells differing in their ultrastructure and spatial location within the colony. The types of cells occurring within a given colony were found to depend on the nitrogen compound present in the medium. As a result of our study, morphological features of colonial bacterial communities were identified. The proposed approach can be viewed as a method to describe microbial associations and communities.

Electron-Microscopic Studies of the Colonies of an Alkylsulfonate-utilizing Bacterial Consortium

The light- and electron-microscopic analysis of the colonies of a bacterial consortium capable of utilizing alkylsulfonates, which are the main ingredients of waste from the synthetic rubber industry, revealed the presence of eight types of cells. All types of cells were gram-negative and differed in shape, size, and the presence of capsule and cytoplasmic inclusions. Three types of cells were present in all the colonies studied. The presence of the other types of cells depended on the inoculum used and on the composition of the growth medium.

Application of Biotechnology to the Problem of the Disposal of Radioactive Wastes

Artificial biological systems are proposed for use in the treatment of low- and intermediate-level radioactive wastes. The microbial conversion of organic and inorganic substances under continuous conditions, involving the turnover of matter, will allow a significant reduction in volume of radioactive wastes. Such specialised systems can act as a biogeochemical barrier for radionuclide transport.