[The possible mechanisms of the adaptation of microbial populations to low positive temperatures]. / Vozmozhnye mekhanizmy adaptatsii mikrobnykh populiatsii k nizkim polozhitel'nym temperaturam.

Biologically low temperature was studied for its effect on the survival of populations and their biochemical and molecular-genetical state. The research was carried out on Yersinia pseudotuberculosis and Shigella sonnei models. It is established that the process of low-temperature adaptation of the populations may occur either at the level of the whole population with participation of inducible cold isoenzymes or at the level of a part of population, the temperature being a selection factor of the adapted cells.

[Various approaches to studying molecular-genetic mechanisms of low-temperature adaptation of microbial populations]. / Nekotorye podkhody k izucheniiu molkuliarno-geneticheskikh mekhanizmov nizkotemperaturnoi adaptatsii mikrobnykh populiatsii.

The effect of biologically low temperature (12 degrees C) on the parameters of microbial population such as survival, catalase activity and its isoenzyme spectrum have been investigated on the models of Escherichia coli and Yersinia pseudotuberculosis. The quantity of nucleic acids, plasmid spectrum and temperature effect on the level of plasmid DNA spiralization were studied under these conditions. The process of molecular genetic adaptation of bacterial populations having the broad temperature limits of growth and demonstrating the increased genetical expression when affected by the biologically low temperature has been found to be regulated on the transcriptional level. The inducible catalase isoenzymes participate in adaptation. The effect of biologically low temperature on the level of the plasmid DNA superhelicity and DNA quantity during the short period of poststress was not demonstrated.

[Differential isolation of low-molecular plasmids]. / Differentsitovannoe vydelenie nizkomolekuliarnykh plazmid.

Several methods for the isolation of plasmid DNA from Yersinia pseudotuberculosis have been tried; the aim of the study has been a differentiated isolation of low-molecular plasmids from natural strains of bacteria containing plasmids with various molecular masses. The modifications of the known methods have been developed, that rule out the use of lysozyme for cell lysis and permit prepare clarified lysates containing mostly low-molecular plasmid DNA from natural strains of bacteria containing high-molecular plasmids as well.

[Origin of invaginations and vacuoles in liposomes under the effect of endocytosis inducers including oxidants]. / Voznikhovenie invaginatsii i vezikul u liposom pod vliianiem induktorov éndotsitoza, v tom chisle oksidantov.

The action of various substances on the morphology of multilayer membranes made of lipids of egg yolk was studied. It has been shown that electroneutral and anionic compounds scaresly affected liposomes, whereas substances with pronounced basic properties, i.e. peroxidase, hemoglobin, cytochrome c, and RNAase, as well as lanthanium ions, induced the formation of invaginations, vesicles and aggregation of liposomes. Metals with variable valency: Cu2+, Cu4+, Ru6+, including lipid oxidants Fe3+ and UO+, produced similar morphological changes more intensely and moreover destroyed liposomal membranes. The activator of lipid peroxidation, namely ascorbic acid, intensified while antioxidizers such as alpha-tocopherylacetate and ionol removed the action of Fe3+ on liposomes. A protective effect was displayed by Ca2+ and Mg2+ ions and due to an increase in pH medium. Since many tested substances with the basic properties stimulate endocytosis of cells the processes of lipid peroxidation and electrostatic interactions are supposed to be part of endocytosis mechanism which does not involve the metabolic energy. It is also assumed that endocytosis may arise at the stage of protocells in terms of evolutions.