Biomedical subjects

N S Pechurkin

Publications and source records attributed to N S Pechurkin.

49 records · Page 3Linked to original sources

PubMedDate not supplied

[Factor of salinity and adaptive capacity of recombinant strains of Escherichia coli and Bacillus subtilis].

Effect of different concentrations of salts on natural and recombinant strains of Bacillus subtilis and Escherichia coli was studied. The recombinant strain of B. subtilis was found to be more osmotolerant than the wild-type strain of this bacterium, whereas the opposite situation was observed for the recombinant and wild-type strains of E. coli. Some salts exerted a bacteriostatic effect on E. coli and B. subtilis. The adaptive capacity of recombinant strains depended on the number of plasmid copies in the cells. The introduction of recombinant bacteria into model ecosystems resulted in the generation of their variants with increased osmotolerance.

Adaptation, Biological↗

PubMedDate not supplied

[The study of heterogeneity of plasmid-bearing and plasmid-f ree populations of Bacillus subtilis under different environmental conditions].

The population heterogeneity of recombinant and plasmid-free Bacillus subtilis strains introduced into aquatic microcosms was studied. After introduction, the population of the plasmid-free strain B. subtilis 2335 in microcosms has long been represented by both vegetative cells and spores, whereas, already ten days after introduction, the population of the recombinant strain B. subtilis 2335/105 (Km[symbol: see text]nf+) was represented only by spores. The number of plasmid copies in the spore isolates of the recombinant strain was the same as before introduction, but the plasmid abundance in the vegetative isolates of this strain decreased. The isolates of B. subtilis 2335/105 obtained from microcosms and the variants of this strain obtained by ten successive subcultures on M9 and 0.1 x M9 media with and without kanamycin (Km) differed in the number of plasmid copies, Km resistance, and maximum biomass yield during batch cultivation. Irrespective of the presence of Km, more than 50% of the variants subcultured on M9 medium showed reduced plasmid abundance. At the same time, about 70% of the variants subcultured on 0.1 x M9 medium with Km and 90% of the variants subcultured on the same medium without Km retained the initial number of plasmid copies. The variants subcultured on media with Km retained the initial biomass level. In more than 70% of the variants isolated from media without Km, the biomass yield increased.

Bacillus subtilis↗

PubMedDate not supplied

[Mathematical modeling of population dynamics of unstable plasmid-containing bacteria during continuous cultivation in a chemostat].

A structural approach to studying the regularities of the population dynamics of unstable recombinant bacterial strains in a chemostat was elaborated. The approach is based on the mathematical modeling of cell distribution in a population with different numbers of plasmid copies. The effect of decreased selective preference of plasmidless variants of the recombinant strain in the chemostat, which is related to a decrease in the number of plasmid copies in cells upon long-term incubation was analyzed. It is shown that the time of half-elimination of plasmids from the bacterial population in the steady state in the chemostat T1/2 does not depend on the maximum number of plasmid copies in cells N but is determined only by the mean time of generation g and the probability of the loss of one plasmid copy tau. The dependence of the preference of bacterial plasmidless variants on the efficiency of expression of genes cloned into plasmids in chemostat was analyzed using the recombinant strain E. coli Z905, whose plasmids pPHL-7 contain cloned genes for the luminescence system of marine luminescing bacteria Photobacterium leiognathi.

Bioreactors↗

PubMedDate not supplied

[Stability of recombinant plasmids in transgenic microorganism cells under various environmental conditions].

The copy number of R plasmids weakly depends on the selective pressure of the respective antibiotic but does depend on the physiology of the host species and the type of plasmids and cloned genes, whose expression leads to a further load on the biosynthetic apparatus of cells. The last factor is critical in the maintenance of recombinant plasmids in transgenic microorganisms.

Bacillus subtilis↗

PubMedDate not supplied

[Mathematical model of the interaction of components in a plant-rhizospheric microorganisms system at the higher level of carbon dioxide in atmosphere].

A mathematical model describing the interaction of plants and rhizospheric microorganisms on complete mineral medium at a higher CO2 level in the atmosphere was constructed. The positive effect of CO2-enrichment on the system plant--rhizospheric microorganisms was shown. The effect of rhizospheric microorganisms on plant growth at normal and high level of carbon dioxide was demonstrated. It was shown that the biomass of plant in the system is smaller than the biomass of plant growing without microorganisms. It was experimentally demonstrated that a simple ecosystem wheat--Pseudomonas putida--artificial soil develops and functions differently than its individual constituents in the case of a wheat-artificial soil system. With unlimited nutrition and a higher CO2 level (0.06%), plants with roots inoculated with microorganisms have a smaller biomass than plants that were not inoculated with microorganisms.

Algorithms↗

PubMedDate not supplied

[Dynamics of the population structure of the Escherichia coli recombinant strain during continuous culture].

The populational structure of the Escherichia coli strain Z905 containing the recombinant plasmid with the phenotype AprLux+ was studied in chemostat. It was shown that the stability of the ratio of plasmid containing cells and cells without plasmids depends in the first place on the presence of the selective factor (ampicillin) in the medium and on the sources of carbon and energy limiting growth.

Ampicillin↗

PubMedDate not supplied

[Candida mycoderma growth inhibition with phenol and the autoselection of resistent forms under continuous pH-stat cultivation].

The effect of phenol on the growth rate and respiration was studied with the yeast Candida mycoderma cultivated in the pH-static conditions with continuous recording of the principal kinetic parameters of the population. The kinetics of growth inhibition with phenol was studied. Adaptation of the culture in terms of the growth rate and the rate of oxygen uptake was detected within 10--15 hours of cultivation. A new strain of C. mycoderma Phen. R. isolated using the technique of autoselection upon continuous cultivation for a long period of time, at a phenol concentration of 1.5 g/l in the growth medium, had an elevated growth rate (2.2 times higher) in these conditions as compared with the parent culture and required less oxygen.

Adaptation, Physiological↗

PubMedDate not supplied

[Comparative analysis of evolution of Eigen's hypercycles and microbial populations in open systems].

The models of evolution of Eigen's hypercycles and microbial populations were compared. It has been proved that both above mentioned model descriptions of evolution completely coincide for the case of support constant organization (1). It has been shown that in the case of constant flows (2) for the Eigen's model it is necessary to take into account the dynamics of concentration of energy monomers. The experimental results of microevolution of microbial populations for conditions 1 and 2 are presented.

Bacteria↗

PubMedDate not supplied

[Substrate inhibition and Candida tropicalis growth limitation by phenol in continuous chemostat and pH-stat cultures].

The aim of this work was to investigate phenol decomposition by Candida tropicalis 29-10 adapted to phenol as a sole source of carbon and energy, and to elucidate the nature of resistance of continuous cultures decomposing phenol in processes with two types of control, viz. in chemostat and in pH-stat. The results suggest the resistance of the pH-stat regime of microbial cultivation during substrate inhibition. A region of instability in the chemostat cultivation has been determined when the yeast growth was inhibited with phenol.

Adaptation, Physiological↗

PubMedDate not supplied

[Interaction in the phage-bacterium system].

The growth rate of the phage for Brevibacterium was studied as a function of the population of the host bacterium and its growth rate. The interaction was not additive when the phage-bacterium system was modeled in chemostat and in periodic regime. This fact was taken into account to describe more precisely and completely the qualitative characteristics of such a system as compared to models of the predator-victim type.

Bacteriophages↗

PubMedDate not supplied

[Phenotypic variability of a recombinant luminescent strain of Escherichia coli in water microcosms].

The behavior of Escherichia coli Z905, carrying a recombinant plasmid pPHL7 with genes determining ampicillin resistance and bacterial luminescence, and the efficiency of expression of cloned genes were studied after introduction of the strain into model aqueous ecosystems with different trophic chain lengths. The E. coli Z905 variants isolated from ecosystems after different periods of time were found to vary in their resistance to ampicillin (from 50 to 0.05 micrograms/ml) and in the intensity of bioluminescence. An increase in the concentration of the selective factor (ampicillin) or in the extent of the aqueous microcosm blooming restored the expression of the recombinant plasmid genes in some clones.

Ampicillin Resistance↗

PubMedDate not supplied

[Change in regulation of catabolite-dependent lux-operon, cloned in a recombinant plasmid, under the effect of environmental factors].

Expression of the lux-genes cloned on the recombinant plasmid pPHL7 (AprLux+) in Escherichia coli z905 cells was studied in various environments, including model aquatic ecosystems. Expression of the lux-genes strongly depended on the nutritional status of the medium. In particular, the cultivation of cells in nutrient-rich medium favored the maintenance of the initial level of expression of the lux-operon, whereas nutrient limitation induced recombinant cell variants with an impaired control of the catabolite-dependent lux-operon. On the other hand, long-term laboratory cultivation of recombinant strain in nutrient-deficient media or its long-term life in model aquatic ecosystems led to the accumulation of cells with a stringent control on the cloned lux-genes in the bacterial population. The presence of the selective factor (ampicillin) in the medium had no significant effect on the expression of the lux-operon.

Cloning, Molecular↗

PubMedDate not supplied

[Introduction and long-term storage of recombinant luminescent Escherichia coli strain Z905 in laboratory water microecosystems].

We studied preservation of recombinant Escherichia coli strain Z905 (AprLux+) in liquid microecosystems (LME) after the introduction. E. coli cells were shown to remain viable and preserve the ability to express the cloned lux genes for a long time (more than a year) in LME. The majority of the clones have reduced efficiency of the expression due to either changed regulation of the lux operon or decreased number of copies of the plasmid. These mechanisms could be realized either independently or simultaneously depending on LME conditions. We have exposed the major factors affecting the metabolic activity of the E. coli strain Z905 (AprLux+) introduced into model ecosystems and the level of expression of the cloned genes.

Escherichia coli↗