[COMPARATIVE ANALYSIS OF THE MLVA25- AND MLVA7-TYPING ACCORDING TO THEIR ABILITY TO ASCERTAIN FOCAL AFFILIATION OF YERSINIA PESTIS STRAINS BY THE EXAMPLE OF ISOLATES FROM THE CENTRAL-CAUCASIAN HIGHLAND NATURAL PLAGUE FOCUS].

Comparative analysis of the MLVA25- and MLVA7-typing ability to evaluate focal belonging of Y. pestis strains by the example of bv. medievalis isolates from the Central-Caucasian highland natural plague focus was carried out. The MLVA25-types of-82 isolates from this area were determined and included into the database containing information on 949 Y. pestis strains from other natural foci of Russia and other countries. Categorical-UPGMA dendrograms were created on the bases of the data concerning all 25 VNTR loci or only seven of them, which were recommended by the experts of the Russian Research Anti-Plague Institute "Microbe" for differentiation of the Y. pestis strains according to their affiliation to specific foci. The obtained data indicated greater possibility of diagnostic mistakes in the case of the MLVA7-typing and supported expediency of division of the Central-Caucasian highland natural plague focus into two sub-foci.

[The effect of the osmotic pressure of the culture medium on cells of Francisella tularensis vaccinal strain 15]. / Vliianie osmoticheskogo davleniia kul'tural'noi sredy na kletki vaktsinnogo shtamma 15 Francisella tularensis.

The dependence of the growth rate of F. tularensis on the osmotic properties of the medium can be presented as a curve with the maximum in the area of 500-600 mOsm. Under these circumstances the intracellular osmotic pressure exceeds the extracellular one by 50-100 mOsm. With the rise of the osmotic pressure in the medium the increase of the concentration of K+ in the cells occurs. The energy-dependent accumulation of K+ in the cells at rest is activated by the rise of the osmotic pressure in the medium. F. tularensis are probably capable of osmoregulation, ensured by the energy-dependent osmosensitive K(+)-transporting system.

[A rapid method for determining the viability of Escherichia coli cells subjected to the action of low temperatures]. / Ekspressnyi metod opredeleniia zhiznesposobnosti kletok Escherichia coli, podvergnutykh deistviiu nizkikh temperatur.

When Escherichia coli cells are frozen at a low temperature, various damages appear in them, in particular, in the membranous apparatus. Only stable disorders in the barrier properties of the cytoplasmic membranes are of a critical importance for the cell viability. These disorders should be taken into account when express methods are developed for assaying the viability of bacterial cells. Critical structures (properties) are to be revealed by their analysis after varying the intensity (dose) of the main damaging factors. Provided that the critical feature of each cell has two states (damaged and intact) after the action of extreme factors, its quantitative change correlates in a linear mode with the number of viable cells in the population.

[Nephelometric parameters of plasmolytic reactions in Escherichia coli K-12]. / Issledovanie nefelometricheskikh parametrov plazmoliticheskoi reaktsii bakterii Escherichia coli K-12.

Nephelometric parameters of plasmolysis in Escherichia coli K-12 are presented. The relationship between these parameters and intracellular osmotic pressure, barrier properties of the cytoplasmic membranes and transport of inorganic ions was investigated in the present work. The nephelometric parameters can be used for quantitative estimation of the physiological state of the bacteria.

[Effect of low temperature shock and extracellular ice formation on the external and cytoplasmic membranes of Escherichia coli cells]. / Deistvie shoka, vyzvannogo nizkoi temperaturoi, i vnekletochnogo obrazovaniia l'da na vneshniuiu i tsitoplazmaticheskuiu membrany kletok Escherichia coli.

The effect of low temperature shock and extracellular ice formation on the properties of the outer and cytoplasmic membranes of E. coli K-12 cells was studied. The shock released intracellular K+ ions and inhibited the respiratory activity of the cells, suggesting that the cytoplasmic membrane was damaged. Crystallization of extracellular water caused additional disorders of the cytoplasmic membrane. Damages of the outer membrane detected by permeability for ethidium bromide appeared only after extracellular ice formation. The outer membrane of E. coli was not susceptible to a cold shock.

[Permeability of the membrane of the Escherichia coli envelope for ethidium bromide]. / Issledovanie pronitsaemosti membran obolochki Escherichia coli dlia bromistogo étidiia.

The interaction of ethidium bromide, a fluorescent dye, with Escherichia coli cells was studied. The envelope of intact cells was shown to be impermeable for ethidium bromide molecules. The dye penetrated however into E. coli spheroplasts. The barrier properties of the cell envelope against ethidium bromide were ruptured if the cells were treated with EDTA. The results suggest that the outer membrane serves as a principal barrier against penetration of ethidium bromide inside the cells while the cytoplasmic membrane of E. coli is permeable for the dye.