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I L Rabotnova

Publications and source records attributed to I L Rabotnova.

18 recordsLinked to original sources
PubMed1977

[Effect of Cu++ ions on the morphological, cytological, and physiological state of Candida utilis cells in continuous culture].

Cells of Candida utilis grown in continuous culture under the influence of rather high concentrations of copper ions have been studied biochemically, morphologically, and cytologically. Although under these conditions a new steady state has been adjusted, the population is much more differentiated than under control conditions. With regard to their size, structure, and viability the cells have been arranged into 4 groups. Generally, the "copper cells" in comparison with the "normal cells" are more voluminous (average: 2.5 times; maximum: 4 times) and of altered structure. The appearance of dense particles ("copper containing particles"), globules ("lipid globules"), vacuoles, and the thickening of the cell wall, as well as the disappearance of the mitochondrial cristae have been shown as characteristic indications for damage in the cell substructure caused by the influence of copper ions. Occasionally abnormal cell shapes can be observed. A permanent influence of copper ions in the concentration used was followed also by striking disturbances of the cell metabolism. The cells take up more carbon, phosphorus, and nitrogen, whereas protein synthesis and respiratory activity decrease. Both the synthesis of lipids and polysaccharides and the phosphohydrolase activity increase. A discussion of the experimental data is presented.

Candida↗
PubMedDate not supplied

[Tolerance to H202 of Mycobacterium carotenum and its carotinoidless mutant].

Mycobacterium carotenum is more tolerant to the action of hydrogen peroxide than its white, carotenoidless mutant. This elevated tolerance to H2O2 correlates with a higher content of DNA, RNA, and polysaccharides in the cells; it is not related to the content of proteins and lipids, or to the level of the catalase and peroxidase activity.

Bacterial Proteins↗
PubMedDate not supplied

[Transitional state of Candida utilis chemostat culture after shock caused by a low pH value of the medium during 1 generation].

Transitional states of Candida utilis BKM Y-1668 were found during its growth in conditions of chemostat at D of 0.1 hr(-1) and glycerol limit after a shock caused by an extreme pH value (2.2). The optical density of the cells, the amount of dry biomass and protein, the activity of respiration, the content of ATP, and the activity of ATPase decreased, the character of the decrease being that of damped oscillations. Qualitative changes were detected in the activity of respiration, oxygen uptake was not inhibited by cyanide. More glycerol and phosphorus are utilized in processes of vital activity. Therefore, a sharp change of pH values causes profound changes in the metabolism of the yeast cell.

Adenosine Triphosphatases↗
PubMedDate not supplied

[Physiologo-biochemical properties of a chemostatic culture of Bacillus megaterium at different pH values].

Properties of the chemostat culture of Bacillus megaterium were studied during its growth in the state of stress caused by unfavourable acid and alkaline values of pH. The effect of pH is not specific since changes occur in both energy exchange and constructive metabolism. The common action of hydrogen and hydroxyl ions is a decrease in the economic coefficient as greater amounts of the energy substrate are being used, the repression of oxidative enzymes, a decrease in the pool of ATP, and an increase in the respiration quotient. Protein synthesis is inhibited and synthesis of nitrogenless reserve substances is stimulated. Acid and alkaline conditions have also a specific action in the cells of Bac. megaterium. In the alkaline medium, metabolites are liberated into the medium, the cells are enriched with carbohydrates, and acetate is accumulated in the medium. In the acid medium, the cells are enriched with acid insoluble polyphosphates. Idle consumption of the energy substrate takes place.

Bacillus megaterium↗
PubMedDate not supplied

[Effect of H+ and OH- ions on the physiological and biochemical properties of a Pseudomonas methanolica culture].

The growth of Pseudomonas methanolica was inhibited by unfavourable values of pH in the conditions of chemostat; the rate of the substrate assimilation was higher, and anabolic and catabolic reactions were decoupled. Hydrogen ions inhibited the activity of enzymes of the Krebs cycle, hydroxyl ions inhibited the activity of methanol dehydrogenase. Changes in pH are presumed to involve the energy apparatus of the cell membrane.

Alcohol Oxidoreductases↗
PubMedDate not supplied

[Effect of pH values of the medium unfavorable for growth on the physiological, morphological and cytological characteristics of a chemostat culture of Candida utilis].

The effect of growth inhibiting values of pH of the medium (pH 2.3 and 7.8) on physiological, morphological and cytological characteristics was studied with the chemostat culture of Candida utilis. Changes in the pH of the medium were accompanied with a decrease in the economic coefficient of the yeast cells, an increase in the respiratory quotient and the activity of phosphohydrolase. Phase-contrast micriscopy has shown that, at acid pH values, the cells were smaller than in the control (in the cells grown under optimal conditions) and rather uniform, oval or rounded, and contained large lipid granules. The presence of large lipid granules was confirmed by electron microscopy; vacuoles were smaller than in the control cells, but their number was greater than one; mitochondria stuck together and had one general outer membrane; the cell wall was 3--4 times thicker. At alkaline pH values of the medium, the whole cellular organization of C. utilis was disordered: the cells were larger, the size of vacuoles increased too much, and the structure became heterogeneous.

Candida↗
PubMedDate not supplied

[Effect of the redox potential on the growth of aerobic microorganisms].

The effect of redox potential was studied on the growth of the following aerobic microorganisms: Candida utilis, Bacillus megaterium, Pseudomonas fluorescens. The action of oxidizing agents (K3Fe(CN)6, KIO3, K2Cr207 and KMnO4) and reducing agents (ascorbic acid, sodium thioglycolate, K4Fe (CN)6 and Na2S2O3) on the growth rate was investigated. K3Fe(CN)6, ascorbic acid, sodium thioglycolate and K4Fe(CN)6 were found to be suitable for buffering the Eh of the medium. The potential could be shifted by 50--200 mV by adding various reducing and oxidizing agents. The rate of growth of C. utilis, Bac. megaterium and Ps. fluorescens did not depend on the potential value.

Aerobiosis↗
PubMedDate not supplied

[Principle growth indices of a chemostat Candida utilis culture resistant to acid pH values].

The kinetics of growth of the Candida utilis chemostat culture 1668-3-37 was studied in a synthetic medium with ethanol at different values of pH and temperature. Chemostat curves were obtained for the pH of the medium of 4.5 and 3.0 and the temperature of 32 degrees C. The following growth characteristics were determined: the maximal growth rate (mumax), the economical coefficient (Y), the substrate (saturation) constant (Ks), the rate of ethanol uptake (q), maintenance energy (m). The minimal amount of ethanol inhibiting the yeast growth was assayed in short-term experiments under periodic conditions with shaking. The value of mumax was 0.35 hr-1 when the yeast was cultivated at 32 degrees C and the pH 4.5, and 0.32 hr-1 at the pH 3.0. The value of Ks varied by an order of magnitude at different pH values when the chemostat culture was grown at D=0.2 hr-1: 36.0 mg/litre at the pH of 3.0 and 3.75 mg/litre at the pH of 4.5. The value of m was close to 0 at the pH of 4.5 and equaled 5--7 mg of ethanol per gram of dry biomass per hour at the pH of 3.0; it was still higher when the temperature of cultivation was increased to 38 degrees C. The minimal substrate (ethanol) concentration inhibiting the yeast growth was constant at different cultivation conditions (pH 3.0 or 4.5 and temperature 32 or 38 degrees C), being equal to 0.45% (v/v) of ethanol.

Candida↗
PubMedDate not supplied

[Cell adhesion in a chemostat culture of Candida utilis under the influence of supraoptimal temperature and elevated acidity].

The effect of the supraoptimal temperature (38, 40 degrees C) on the chemostat culture of Candida utilis was studied. The above factor caused a part of the biomass to float as a thin layer of foam to the surface of the medium. After an hour, the concentration of the cells on the surface could be four times as high as that within the medium. The content of protein was the same in the cells taken from the surface and from the depth. Singular cells or their groups (2 or 4--8 cells) were found deep in the medium whereas cells on the surface were aggregated forming conglomerates of 20--100 and more cells. The simultaneous action of the elevated tmperature and the acid pH value made flotation of cells onto the surface more stable and protracted (it could be maintained in a chemostat for weeks).

Candida↗
PubMedDate not supplied

[Binding of silver ions by Candida utilis cells].

Binding of silver ions by the cells of Candida utilis involves their adsorption on the cell surface. It was found that 90% of all silver bound by the cells was localized in the fraction of cell walls and cytoplasmic membranes. The sensitivity of protoplasts to the toxic action of silver ions is much higher than that of intact cells. The toxic effect of silver ions is supposed to be related to changes in the functions of cytoplasmic membranes.

Binding Sites↗
PubMedDate not supplied

[A mathematical model of inhibition of the growth of Candida utilis by heavy metal ions].

A mathematical model described in this paper, contrary to other models, takes into account transport effects during penetration of the inhibitor into the cell of a micro-organism, and also a possibility of partial inactivation of the inhibitor during formation of complexes. It changes into models of Monod and Monod--Jerusalimsky at extreme values of parameters. Theoretical steady-state concentrations of the biomass in chemostat predicted on the basis of this model coincided with values obtained in experiments with limitation of growth of Candida utilis by silver ions and copper ions.

Candida↗