[Methods of microorganism immobilization for dynamic atomic-force studies (review)].

Atomic-force microscopy (AFM) is an efficient method for studying the surface ultrastructure and nanomechanical properties of biological objects (including microorganisms). A correctly selected method of microorganism immobilization (that provides a strong attachment of cells on the surface of a biologically inert substrate and the preservation of their native properties) is an important condition of AFM scanning in a liquid medium. Comparative characteristics of methods of microorganism immobilization (that are applied in dynamic AFM studies) are given in the review. Technologies of mechanical retention and chemical binding of cells to a substrate, as well as protein and immunospecific adsorption, are considered.

[Distribution of internal parameters of protein hydration shell structure].

Valence and torsion angles distribution was obtained by computer simulation for protein hydration shell and bulk water. These distributions were analyzed. Hydration shell and bulk water have different distributions and we explain it in terms of topology.

[Effect of cultivation conditions on the adhesive activity of rhodococci towards n-hexadecane].

The effect of cultivation conditions (the composition, acidity, and salinity of the cultivation medium; temperature; and the hydrodynamic conditions of cultivation) on the adhesion of actinobacteria of the genus Rhodococcus to n-hexadecane has been investigated. A study performed showed that the adhesive activity of rhodococci depends on the composition of the cultivation medium and on the cultivation temperature. The possible mechanisms underlying the effect of growth conditions on the adhesion ofrhodococci to liquid hydrocarbons and involving changes in the cell lipid content or the zeta potential of cells are addressed. Rhodococcal strains displaying high adhesive activity (80-90%) at a low temperature (18 degrees C), high salinity (5.0% NaCl), and acidity (pH 6.0) of the cultivation medium have been selected as a result of the present work; these strains have a considerable potential for use in bioremediation of soil and water contaminated by hydrocarbons.

[Adsorptive immobilization of rhodococcal cells in hydrophobized derivatives of wide-pore polyacrylamide cryogel].

Adsorption of Rhodococcus ruber cells on columns with polyacrylamide cryogel (CryoPAAG) partially hydrophobized by different quantities (0.2, 1, and 5 mol %) of chemically grafted n-dodecane residues has been studied. The adsorption capacity (1.1 x 10(9) cells/g) of gel carrier for rhodococcal cells and the optimal content (1 mol %) of hydrophobizing groups were determined. The respirometric method showed the high catalytic activity and functional stability of immobilized bacterial cells. Respiratory activity of immobilized rhodococci in the presence of a model mixture of oil hydrocarbons exceeded the respective parameter for free cells by 12-17%. Viability of rhodococcal cells adsorptionally fixed in hydrophobized cryoPAAG was maintained at a level of 93-95% after a half-year period of storage. The results may be used for development of immobilized biocatalyst for directed transformation of hydrocarbon compounds and biological purification of oil-polluted water.

[Actinomadura species as antibiotic producers]. / Vidy roda Actinomadura kak produtsenty antibiotikov.

Screening of antibiotic-producing cultures among Actinomadura showed that definite species mainly produced antibiotics of the same groups. Thus, carminomycins were produced by all the 4 studied strains of A. carminata, maduramycins were produced by 3 strains of A. rubra, prodigiozines were produced by 3 strains of A. madurae and luzopeptines were produced by 6 strains of A. recticatena. Supposedly, new antibiotics with original spectral characteristics were isolated from 2 strains of A. fulvescens. There was a clear-cut relation of the number of the active strains and their antibiotic productivity in definite media to their species. The liquid nutrient media, such as yeast-sucrose, soya-glucose and soya-glucose with cobalt chloride proved to be the most efficient in the primary screening of antibiotic-producing cultures.