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V G Bulgakova

Publications and source records attributed to V G Bulgakova.

At least 19 recordsLinked to original sources
PubMed1993

[Comparative study on the activity of some enzyme systems in cells of gramicidin S sensitive and resistant strains of Staphylococcus aureus].

Polarographic determination of the rate of endogenic respiration of the cells of Staphylococcus aureus 209P showed that the respiration activity of the cells of the strain resistant to 20 micrograms/ml of gramicidin S was 20 to 30 per cent lower than that of the sensitive strain. The rate of oxygen consumption in oxidation of NADH by the membrane preparations of the resistant cells was also 25 to 30 per cent lower. By comparison with the initial sensitive strain the activity of endogenic DPI-reductases of the intact cells and NADH-dehydrogenases of the membranes of the resistant strain was also lower. The velocity of the valine transport to the resistant cells was much lower than that of the amino acid transport to the cells of the sensitive strain. Development of gramicidin S resistance in the staphylococcal strain was likely accompanied by a decrease in the activity of the energy metabolism in the membranes.

Amino Acids↗
PubMed1989

[Study of the adaptation resistance in bacteria to membrane active polypeptide antibiotics].

Variants of Micrococcus lysodeikticus resistant to 100 micrograms/ml of gramicidin S with preserved resistance in subcultures on media without the antibiotic were isolated as a result of prolonged adaptation on a solid medium with increasing concentrations of gramicidin. The sensitive and resistant cells did not differ by their ability to bind gramicidin. Under the antibiotic effect permeability of the cytoplasmic membranes of the intact cells in the sensitive bacteria appeared to be impaired to a greater extent than that of the membranes of the cells in the resistant variant. Comparison of the lytic activity of gramicidin and its derivatives with respect to the protoplasts prepared with the cells of the initial and resistant variants of M. lysodeikticus revealed much higher resistance of the resistant variant protoplasts to the membrane-disorganizing effect of the preparations. Malate dehydrogenase and NADH-oxidase in the membrane preparations of the resistant variant cells differed from analogous enzymes from the membranes of the initial strain by the levels of their activity and sensitivity to gramicidin. It is likely that during adaptation of M. lysodeikticus to gramicidin significant changes in the cell cytoplasmic membranes occurred.

Adaptation, Physiological↗
PubMed1988

[The action of gramicidin S on the ionic permeability of bilayer lipid membranes].

The effect of cyclic decapeptide of gramicidin S on electrical conductivity of bilayer lipid membranes has been studied. The integral conductivity of bilayer has been shown to increase with the growth of antibiotic concentration. The integral conductivity increase occurs as series of conductivity discrete leaps, differing in amplitude from fluctuations of conductivity caused by linear gramicidins. In the series of selectivity of bilayer membranes for cations of alkaline metals the rubidium ion is before the cesium ion. This is the only difference between this series and the series of relative ionic mobility series of cations of alkaline metals in water solutions.

Cell Membrane Permeability↗
PubMed1988

[Physicochemical mechanisms of the action of gramicidin S on a model membrane].

Influence of gramicidin S on electric parameters of nitrocellulose ultrafilter as a biomembrane model was studied, the ultrafilters being impregnated with fatty acids or their ethers. It was shown that addition of the antibiotic to the solution over one side of the model membrane resulted in generation of electric potential. With increasing of the drug concentration by one order there was observed more than a 10-fold drop in the membrane resistance while the electric capacitance actually remained unchanged. It was suggested that gramicidin S was localized in thin water layers covering the surface of the ultrafilter pores and separating the polymer matrix and impregnating liquid filling the pores. Such incorporation led to changes in the state of water and water channel surfaces which defined the increase in the model membrane electric conductivity.

Chemical Phenomena↗
PubMed1988

[Effect of salts on the lytic activity of gramicidin S and its derivatives].

Potassium and sodium chlorides, sulfates, acetates and phosphates activated the lytic action of gramicidin S and its derivatives on protoplasts of M. lysodeikticus. The derivatives used were positively charged and neutral by the free amino groups in the ornithine moieties. The salts had no effect on lysis of the bacillar protoplasts by gramicidin S and its positively charged derivatives. The lytic effect of the neutral derivative on the bacillar protoplasts markedly increased in the presence of the salts, activation of the lysis by the phosphates being more pronounced than that by the other salts. Increased membrane activity of gramicidin S in the presence of the salts was not connected with association of the substance molecules in solution. Probably it was due to increased destruction of the membranes at the account of activated detergent effect of the antibiotic and its derivatives.

Bacillus subtilis↗
PubMed1987

[Action of thomicide on bacterial cells. The membranotropic activity of thomicide].

It was shown that a combined drug thomicide impaired permeability of cell membranes in Micrococcus luteus 2665 and Staphylococcus aureus 209P inducing production of substances with the absorption maxima at 260 nm. Active lysis of the M. luteus 2665 protoplasts under the action of thomicide used in a dose of at least 60 micrograms per 1 mg of the protoplast proteins was observed. Thomicide inhibited oxidation of the substrates by intact cells of the staphylococci and micrococci. Respiration of the micrococcal protoplasts was inhibited by thomicide in concentrations inducing lysis of the protoplasts. Impairment of function and the state of the membranes of the bacterial cells (production of compounds with the absorption maxima at 260 nm, protoplast lysis and respiration inhibition) was recorded at thomicide concentrations lower than the bactericidal ones. The membranotropic activity of thomicide was associated with thermostable component of the complex.

Animals↗
PubMed1986

[Effect of the cultivation temperature on gramicidin S biosynthesis under conditions of producer growth limitation by oxygen].

The gramicidin S-producing organisms Bacillus brevis was grown under submerged conditions in fermenters at a temperature of 32 degrees C which is the lower limit of the temperature ranges providing the culture growth. The culture was also grown under the optimal temperature conditions, i.e. 40 degrees C. At the lower temperature the biomass synthesis at the early stage of the culture development was decreased, the intensity of the cell respiration was low and solubility of oxygen in the liquid was increased. Under such conditions the decrease in the levels of dissolved oxygen in the medium was less pronounced than that under the control conditions. At the lower temperature limitation of the culture growth by the deficit of dissolved oxygen lowered and the period of the antibiotic synthesis increased which brought about a rise of the gramicidin S yield by 30-40 per cent.

Bacillus↗
PubMed1986

[Changes in the permeability of streptomycete cytoplasmic membranes due to gramicidin S and its derivatives].

Exposure of intact mycelium and protoplasts of Streptomyces sp. 26-115 to gramicidin S resulted in impairment of permeability of the cytoplasmic membranes thus inducing a loss of low molecular compounds by the cells and protoplasts. Aminoacyl and guanyl derivatives of gramicidin S with respect to the delta-amine group of ornithine were somewhat less effective with respect to the streptomycete membranes. The same as the initial antibiotic, these derivatives had positively charged groups. The changes in the membranes of the streptomycete protoplasts induced by gramicidin S and its derivatives did not result in the protoplast lysis accompanied by decreasing of the suspension optical density. The neutral derivative having no positive charge and not capable of complexing with the membrane phospholipids and the carboxyl-containing derivative with a negative charge showed a low membrane activity when applied to the protoplasts and induced no impairment of permeability of the intact mycelium membranes. The use of phosphates as factors increasing the membrane activity of the gramicidin derivatives having no positive charge is not possible since in the presence of phosphates streptomycete protoplasts are readily destroyed.

Cell Membrane Permeability↗
PubMed1986

[Comparative study of the surface-active properties of gramicidin S and its derivatives by polarography].

Gramicidin S and its derivatives by the free amino groups of the ornithine moieties were studied with respect to their effect on interface tension of mercury and the polarographic background for comparative estimation of the surface active properties of these compounds. The same way as the compounds preserving their main properties, the neutral and acid derivatives lowered the polarographic maximum. No correlation between the level of the antimicrobial and membrane activity and the surface active properties of the tested compounds was observed. It is likely that the direct cause of the induced biological effect is not connected with the surface active properties responsible for possible interaction of the tested substances with the cell (protoplast).

Cell Membrane Permeability↗
PubMed1985

[Superoxide dismutase activity of Bacillus brevis var. G.-B. cells, producer of gramicidin C, in relation to cultivation conditions].

The activity of superoxide dismutase (SOD) in the cells of the microorganisms producing gramicidin S, B. brevis var. G.-B., ranged from 7 to 22 units per mg protein. When the culture was grown in a fermenter, the decrease in the concentration of dissolved oxygen in the medium to the minimum values corresponded to the decrease in the enzyme activity. By the end of the fermentation process, when consumption of oxygen by the culture lowered and its level in the medium increased, the enzyme activity increased. When the culture was grown in flasks, no effect of the medium aeration level on the enzyme activity was noted. This might be associated with rather high levels of dissolved oxygen in the medium in the flasks under all aeration conditions. Addition of manganese ions to the cultivation medium activated SOD in the cells of B. brevis. Synthesis of gramicidin S by the bacterial culture had no effect on the activity of SOD in the cells.

Aerobiosis↗
PubMed1985

[Effect of phosphates on the membrane activity of gramicidin S].

The membrane activity of gramicidin S against intact cells of staphylococci and micrococci determined by the loss of intracellular low-molecular compounds with the adsorption maxima at 260 nm by the bacteria markedly increased in the presence of phosphates. Acetate and hydrochlorides had no effect on the membranotropic action of the antibiotic. Analogous results were obtained for gramicidin S derivatives by free ornithine amino groups possessing basic and antibiotic activity. The increased membrane action of the antibiotic on the cells in the presence of phosphates was probably due to the changes under these conditions in the aggregate state of the substance in solution. With the use of labeled gramicidin S it was shown that centrifugation of the antibiotic solution in a concentration of 50-1000 micrograms/ml at 18000-20000 rpm resulted in sedimentation of a significant part of gramicidin S dissolved in the phosphate buffer. Sedimentation of the drug in aqueous and NaCl solutions was insignificant. The presence of phosphates in the medium had no effect on the quantity of the antibiotic bound to the micrococcal membrane preparations. It is suggested that the increase in the level of cytoplasmic membrane disorganization in the presence of phosphates was due to binding of the antibiotic molecule associations to the membranes and/or additional intermolecular association of gramicidin S bound to the membranes.

Buffers↗
PubMed1984

[Effect of gramicidin S and its derivatives on protoplasts of Bacillus subtilis].

The lysis of Bacillus subtilis protoplasts by gramicidin S, a membrane active antibiotic, and its derivatives was studied according to free amino groups of the ornithine residue. The initial antibiotic and guanylgramicidin , a positive charge-preserving derivative, had a high lytic activity. Succinylgramicidin , a gramicidin S derivative with acid properties, and carbomoylgramicidin , a neutral derivative, actively lysed B. subtilis protoplasts suspended in 1/15 M phosphate buffer solution with sucrose . No lytic activity of succinylgramicidin was observed with respect to B. subtilis protoplasts suspended in an aqueous solution of sucrose. Comparative study on the sensitivity of the protoplasts of Micrococcus lysodeikticus, B. megaterium and B. subtilis to the lytic action of gramicidin S and its derivatives showed in the main a similar character of their interaction with the membranes of the protoplasts of the taxonomically close species (B. megaterium and B. subtilis). It is likely that the specificity of the action of the above substances on the protoplasts of M. lysodeikticus, i. e. a complicated character of the dependence of the lytic action of gramicidin S on its concentration, manifestation of the lytic activity of the neutral and acid derivatives in the presence of phosphates or other salts and in sucrose aqueous solution was mainly defined by the properties of the micrococcal membranes.

Bacillus megaterium↗
PubMed1984

[Optical density changes in bacterial protoplast suspensions exposed to membrane-active antibiotics].

The effect of membrane active antibiotics, such as gramicidin S, its derivatives and carbonyl-conjugated pentaens on suspended bacterial protoplasts resulted in lysis of the protoplasts accompanied by a marked decrease in the optical density (OD) of the suspensions. However, when the drug concentrations were lower than those inducing the lysis, an increase in the suspension OD by 10-30 per cent as compared to the control values of the OD was often observed. The increase in the protoplast suspension OD was most pronounced with the use of the drugs with a relatively low lytic activity or under the conditions lowering the lytic activity of the antibiotics. Under such conditions no agglutination of the protoplasts was observed. The comparative estimation of the protoplast diameters by the method of Klenin et al. in the control suspensions of M. lysodeikticus protoplasts and in the suspensions with a stable increase in the OD showed that the OD increase was associated with swelling of the protoplasts: an increase in the suspension OD by approximately 30 per cent corresponded to an increase in the protoplast diameter by approximately 15 per cent. The observed increasing of the suspension OD must be due to the fact that the membrane active antibiotics induced a decrease in the osmotic stability of the protoplasts not sufficient for their lysis.

Anti-Bacterial Agents↗
PubMed1983

[Structuro-functional properties of the bacteria Bacillus brevis in relation to the accumulation of gramicidin S in cells].

The culture of Bacillus brevis var. G-B R-form was grown in the presence of beta-phenyl-beta-alanine, the inhibitor of gramicidin S synthesis, is characterized by enhanced endogenous respiration and the DPI-reductase activity as compared to the culture synthezising antibiotic. The increased synthesis of the antibiotic in the region of the culture transition from the logarithmic growth phase to the linear one is associated with a decrease in the number of viable cells despite the fact that the culture on the whole does not die but continues to grow. The membranes prepared from young gramicidin S-free cells and from the cells enriched with the antibiotic possess identical electron micrograph images, IR spectra and protein sets as determined by polyacrylamide gel electrophoresis in a Na-DS system. However, in young cell membranes NADH and succinate dehydrogenase are insensitive to gramicidin S and only malate dehydrogenase is inhibited by this antibiotic. In aged cell membranes the activities of all mentioned dehydrogenases are suppressed. Malate dehydrogenase from young cells is weakly inhibited by thyrotrycin obtained from Bac. brevis ATCC 10068; succinate dehydrogenase is entirely insensitive to this antibiotic, while NADH-dehydrogenase is almost completely inhibited by it. The specificity of action on the respiratory chain of peptide antibiotics synthesized by the cells of one strain of Bac. brevis is suggestive of a possible regulatory role of these peptides in the metabolism of the producent. Hence the accumulation of gramicidin S which is adsorbed on the membrane and destroys the respiratory chain function to the cause of the low rate of oxygen uptake by the culture of Bac. brevis var. G-B R-form and of the low activities of DPI-reductases.

Alanine↗
PubMed1983

[Effect of heliomycin on the respiration and oxidative phosphorylation of the liver mitochondria of the rat].

The effect of heliomycin and known uncouplers of oxidative phosphorylation on respiration and oxidative phosphorylation was studied comparatively. Heliomycin, as well as 2,4-dinitrophenol, valinomycin and gramicidin S inhibited the mitochondrial synthesis of ATP. This process was inhibited completely by heliomycin at a concentration of 1.5 x 10(-5) M. The synthesis of inorganic pyrophosphate, the other macroergic compound, was also inhibited by heliomycin, ATPase and pyrophosphatase of uncoupled mitochondria being not inhibited by the antibiotic. Like 2,4-dinitrophenol, heliomycin stimulated the synthesis of ATPase and respiration in intact mitochondria. Probably, heliomycin inhibited the synthesis of ATP and pyrophosphate by uncoupling the processes of respiration and oxidative phosphorylation. It was shown earlier that heliomycin, a specific inhibitor of bacterial RNA synthesis, also affected energy metabolism of bacterial cells by inhibiting the synthesis of ATP and active transport.

Adenosine Triphosphate↗
PubMed1982

[Comparison of the lytic effect of gramicidin S and its derivatives on Bacillus megaterium and Micrococcus lysodeikticus protoplasts].

Essential differences were found between the lytic action of gramicidin S. on Bacillus megaterium protoplasts and that on Micrococcus lysodeikticus protoplasts. When protoplasts were suspended in a sucrose solution in phosphate buffer, the lytic activity of gramicidin S toward B. megaterium protoplasts increased with a rise in the antibiotic concentration; the lytic action of gramicidin S on M. lysodeikticus protoplasts was characterized by a complex concentration dependence. Gramicidin S derivatives lacking basic properties since the amino groups of their ornithine residues were either substituted with urea residues (carbamoyl gramicidin) of acetylated (diacetyl gramicidin) showed a high lytic activity toward the both bacterial species. In contrast to gramicidin S, the derivatives virtually did not change the permeability of cytoplasmic membranes when they acted on intact cells. In the absence of phosphates (when protoplasts were suspended in an aqueous sucrose solution), the lytic activity of gramicidin S decreased while carbamoyl gramicidin and diacetyl gramicidin still were capable of causing lysis of M. lysodeikticus protoplasts though not of B. megaterium protoplasts.

Bacillus megaterium↗
PubMed1982

[Effect of carbonyl-conjugated pentaene-group antibiotics on the oxygen absorption rate of a thymocyte suspension].

When used in concentrations of 10-15 micrograms per 10(8) cells, flavofungin and nigrofungin, carbonyl-conjugated pentaenes lowered the rate of oxygen absorption by thymocyte suspensions in the presence of glucose. Flavopentin inhibited glucose oxidation in higher concentrations. ADP and succinate did not penetrate through the thymocyte membranes and were not oxidized with the cell suspensions. In concentrations of 30 micrograms per 10(8) cells the pentaenes did not change the membrane permeability for ADP. Still, they induced oxidation of succinate by the thymocytes (in the presence of amital). Flavofungin and nigrofungin were more effective with respect to increasing the membrane permeability for succinate as compared to flavopentin. The differences in the membrane permeability for various substrates induced by the antibiotics indicated a definite specific nature of the impairment of the thymocyte cytoplasmic membranes by carbonyl-conjugated pentaenes. The antibiotics tested are very similar as to their chemical structure and physicochemical properties. It is suggested that the differences in the biological activity of these substances are not associated with the presence of definite functional groups but are due to the general configuration of the antibiotic molecules, determining their hydrophilic-lipophilic balance and capacity for interaction with the biological membranes.

Animals↗