Biomedical subjects

T A Voeĭkova

Publications and source records attributed to T A Voeĭkova.

18 recordsLinked to original sources

PubMed2005

[Comparative analysis of in vitro antifungal activity and in vivo acute toxicity of the nystatin analogue S44HP produced via genetic engineering].

New polyene macrolide S44HP was purified from the culture of recombinant Streptomyces noursei strain with engineered nystatin polyketide synthase. S44HP, nystatin (NYS), and amphotericin B (Amph-B) were tested against 19 clinical fungal isolates in agar diffusion assay, which demonstrated clear differences in antifungal activities of these antibiotics. Sodium deoxycholate suspensions of all three antibiotics were subjected to acute toxicity studies in vivo upon intravenous administration in mice. NYS exhibited the lowest acute toxicity in mice in these experiments, while both Amph-B and S44HP were shown to be 4 times more toxic as judged from the LD50 values. While the acute toxicity of S44HP was higher than that of Amph-B, the data analysis revealed a significantly increased LD10 to LD50 dose interval for S44HP compared to Amph-B. The data revealed structural features of polyene macrolides, which might have an impact on both the activity and toxicity profiles of these antibiotics. These results represent the first example of preclinical evaluation of an "engineered" polyene macrolide, and can be valuable for rational design of novel antifungal drugs with improved pharmacological properties.

Amphotericin B↗

PubMed2003

[Development of a system of plasmid transfer in the strains Streptomyces avermitilis ATCC 31272 and Saccharopolyspora erythraea ATCC 11635 by the method of intergeneric conjugation].

A new method of plasmid DNA transfer from the donor strain Escherichia coli S17-1 to the erythomycin-producing strain Saccharopolyspora erythraea and avermectin-producing strain Streptomyces avermitilis via intergeneric conjugation was proposed. The optimal parameters of the method were chosen for increasing the efficiency of crosses and ensuring easily reproducible results. The behavior of the multicopy plasmid pPM803 and the integration vector pTO1 along with a number of new plasmids specially created by us, was examined in these strains. A new plasmid vector (pSI60) capable of integrating into the chromosome of actinomycetes at the integration site of the temperate actinophage phi C31 was constructed. This vector possesses unique sites convenient for cloning and may be stably maintained in exconjugants of S. avermitilis and in the model strain Streptomyces lividans. The gene encoding resistance to spectinomycin and streptomycin was cloned into the vector pSI60 in this strain. For cloning in strain Sac. erythraea, vectors pSI261-280, which integrate into the chromosome via homology with the cloned DNA and can be stably maintained in exconjugants, were constructed.

Attachment Sites, Microbiological↗

PubMed2001

[Effect of the gene for bacterial hemoglobin vhb on the effectiveness of the process of Escherichia coli-Streptomyces interspecies conjugation and production of antibiotics in streptomycetes].

The bacterial hemoglobin vhb gene was cloned from sliding bacterium Vitreoscilla sp. as an element of the system ensuring survival of this microorganism in an environment that contains insufficient amount of oxygen. The vhb gene was transferred from Escherichia coli to some Streptomyces strains, producers of antibiotics, by the method of intergeneric conjugation using conjugative-integrative plasmid vectors pIH1 and pCH2. The stability of plasmid DNA inheritance was analyzed in the genomes of exconjugants. A positive effect of the vhb gene on processes of conjugation and antibiotic production in a number of examined strains was shown.

Anti-Bacterial Agents↗

PubMed1999

[Conjugative transfer of a plasmid from Escherichia coli to various strains of the order Actinomycetales].

The conjugal transfer of autonomous and integrative plasmids from the donor strain Escherichia coli S17-1 to strains of genera Actinomadura, Arthrobacter, Kitasatoa, Micromonospora, Nocardia, Rhodococcus, Saccharopolyspora, and to 16 strains of the genus Streptomyces was demonstrated. The status of plasmids in recipient strains and the stability of their inheritance were analyzed. Plasmids constructed for strains of the genus Streptomyces were shown to function in a large number of strains belonging to the order Actinomycetales. The well-developed system of Streptomyces vector molecules and cloned genes of antibiotic biosynthesis allows their transfer to those microorganisms for which conventional techniques of plasmid transfer by regenerated protoplast transformation or electroporation have not been developed or are inefficient.

Actinomycetales↗

PubMed1997

[Elements of regulatory systems of antibiotic biosynthesis in Streptomyces].

Studies of regulation of antibiotic synthesis involved both basic and applied aspects of biology of antibiotic producers. This paper is a survey of published experimental data and key hypotheses for the regulation of antibiotic synthesis in bacteria of the genus Streptomyces. Summarized data on transcriptional regulatory systems of gene clusters responsible for biosynthesis of some antibiotics in these microorganisms are presented. Results of our previous research of the regulation of antibiotic bialaphos production in the S. hygroscopicus strain are considered as well. On the basis of these results, a hypothetical scheme of the organization of lower levels of the regulatory system of the bialaphos biosynthetic cluster was constructed. It is assumed that an integrase-like product of the brpB gene cloned by the authors mediates transcriptional initiation of this gene cluster.

Anti-Bacterial Agents↗

PubMed1996

[Molecular genetic study of the strain Streptomyces virginiae-- the producer of virginiamycin].

The level and the character of the Streptomyces virginiae virginiamycin-producing strain's resistance to self-produced antibiotic and a number of antibiotics from different groups were determined. S. virginiae was shown to display constitutive and inducible resistance to self-produced antibiotic. The phenomenon of cross-inducible resistance of the strain to virginiamycin and the antibiotics erythromycin, oleandomycin, and thiostrepton was demonstrated. The pTO1 and pVGTB24 plasmids were introduced into the strain by the method of intergeneric conjugation with Escherichia coli. Site-specific integration of the pTO1 vector into the S. virginiae chromosomal attB site without disturbance of growth, differentiation, and productivity of the strain was shown. The multicopy autonomously replicating plasmids pIJ699, pIJ702, pWOR109, and the integrative pZAT22 plasmid were introduced into the strain via electrotransformation of germinating spores. The efficiency of transformation was 1-5 x 10(3) transformants per 1 microgram DNA. The stable inheritance of the plasmids in S. virginiae without structural rearrangements was shown. These results allow the use of these plasmids to clone genes into S. virginiae.

Anti-Bacterial Agents↗

PubMed1994

[Use of a plasmid with integrative function of phage phiC31 for transfer of cloned genes into Streptomyces strains].

Opportunities for application of integrative vectors carrying the attP site and the int gene of the temperate actinophage phi C31 for cloning genes in Streptomyces strains were demonstrated. The behavior of the integrative vectors pZAT22 and pTO1 in the model strain S. lividans TK64 and in the bialaphos-producing strain S. hygroscopicus, respectively, was characterized. Restriction maps of the S. lividans and S. hygroscopicus chromosomal regions containing attB sites were constructed. The bar gene of resistance to bialaphos was incorporated into the chromosome of the model strain S. lividans via the integrative pZAT22 vector, the level of expression of this gene within the chromosome of a heterologous host was determined. The possibility of amplification of the bar gene in the chromosome of the strain S. lividans was shown. The conjugative integrative vector pTO1, which carried the cloned bar gene, was introduced into the bialaphos-producing strain by intergeneric matings of Escherichia coli and S. hygroscopicus. The effect of an additional copy of the gene in the chromosome of S. hygroscopicus on strain resistance and productivity was studied.

Bacteriophages↗

PubMed1994

[Molecular-genetic study of the functional role of the regulatory gene brpB of the bialaphos producer Streptomyces hygroscopicus ATCC21705].

A chromosomal determinant of Streptomyces hygroscopicus, functioning as a positive regulator of the bialaphos-resistance gene bar in the model strain S. lividans, was conjugatively transferred into a bialaphos (BAP) producer through pVGTB24 plasmid. The plasmid is unable to replicate autonomously in S. hygroscopicus, but integrates into its chromosome via homology with the fragment containing this determinant. Integration of pVGTB24 was accompanied by a decrease in resistance of S. hygroscopicus exconjugant clones to the self-produced antibiotic and also by a decrease in their antibiotic productivity.

Anti-Bacterial Agents↗

PubMed1994

[Intergeneric Escherichia coli-Streptomyces conjugation as a means for the transfer of conjugative plasmids into producers of antibiotics chlortetracycline and bialaphos].

A system for introduction of plasmids into industrial producers of antibiotics chlortetracycline and bialaphos using intergeneric conjugation of Escherichia coli and Streptomyces was developed. Low level stability of inheritance of autonomously replicating DNA in recipient strains was shown. Site-specific integration of the conjugative-integrative vector pTO1 provided stable plasmid maintenance within the chromosomes of Streptomyces aureofaciens and S. hygroscopicus. Phenomenon of disturbance in differentiation and antibiotic production, resulting from pTO1 integration into S. hygroscopicus chromosome, was discovered.

Anti-Bacterial Agents↗

PubMed1990

[Determinants of resistance to chlortetracycline and other antibiotics in chlortetracycline-producing strain of Streptomyces aureofaciens].

Data are presented on resistance of Streptomyces aureofaciens strain TB-633 FU--the producer of chlortetracycline (CTC) to autogenous antibiotics and a number of other antibiotics. It is demonstrated that resistance to CTC is specified by ctr genes of constitutive expression as well as by inducible genes. CTC and ethidium bromide may serve as efficient inductors of inducible ctr genes. The induction process is accompanied by increase in antibiotic biosynthesis level. Genes responsible for strain resistance to a number of macrolide antibiotics and thiostrepton are inducible and only function in the presence of appropriate antibiotics in the medium. The action of inducible mtr gene(s) is described in detail. The gene(s) simultaneously ensure increase in resistance to CTC and a number of macrolide antibiotics in the presence of exogenous inductors in media, such as both CTC and macrolide antibiotics. Mutants have been isolated which provide constitutive level of resistance to these antibiotics. A series of ctr and mtr mutants have increased CTC biosynthesis as compared to the initial level. Data on comparative analysis of the results obtained from hybridization of fragments of S. aureofaciens and S. rimosus DNAs to actI and actIII genes, responsible for polyketide synthases' synthesis, demonstrate that genes for CTC and OTC biosynthesis are situated on DNA fragments of similar size. This determines the strategy for cloning ctr and mtr genes as well as genes for CTC biosynthesis from S. aureofaciens.

Chlortetracycline↗

PubMed1990

[Development of the system for protoplast generation in Streptomyces aureofaciens strains--chlortetracycline producers].

Conditions for preparation and regeneration of protoplasts in a commercial strain of the culture producing chlortetracycline and its derivatives were determined. The protoplasting level depended on the conditions of the mycelium cultivation and composition of a regeneration medium. Under the optimal conditions it amounted up to 10(6) protoplasts/ml. A mutant able to form regenerating protoplasts at a rate of 10(9) protoplasts/ml was isolated. An autoinhibition effect in regenerating protoplasts was observed. As a result ofprotoplast generationing, the morphological variation increased and the protoplast antibiotic activity changed within wide ranges. Variants with higher productivity in comparison to that of the initial strain were isolated. Stability of the inherited property of antibiotic production in the variants is being studied.

Cell Count↗

PubMed1981

[Actinophage phi C31 restriction and modification].

Actinophage phi C31 was shown to be insensitive to a number of restriction and modification systems (RM). Phage sensitivity to RM systems of those strains to which phage cannot absorb, may be tested using protoplast transfection. For instance, the absence of phi C13 transfection in Streptomyces griseus Kr15 protoplasts, as compared to efficient transfection in protoplasts of R- M+ mutant of this strain seems to imply the sensitivity of phi C31 to the RM system of S. griseus KR15. Restriction of mutant phi C31 phage modified by S. albus G Rm system has been detected in S. coelicolor A3(2). This effect being dependent on a previous host may indicate that the mutant phage was rendered sensitive to an Rm system of S. coelicolor A3(2).

Bacteriophages↗

PubMed1979

[Identification of the restriction and modification systems in Streptomyces strains].

Host range of actinophage phi C31, VP5 and Pg81 in respect to 109 strains of Streptomyces genus and hybrid strain Rcg2 from the cross S. coelicolor A3(2)XS. griseus Kr was studied. The existence of RM-systems in strains S. griseus Kr15, S. griseus Kr20, Rcg2, S. griseofovillus 43 was shown using phage Pg81. Mutants of Pg81 were observed which to some extent lost snesitivity to RM-system in the strain Rcg2. The presence of RM-system in S. lividans 67 was demonstrated by the phage VP5.

Bacteriolysis↗

PubMed1975

[Hybridization in Actinomycetes].

Ways of transferring genetic information in Actinomycetes and their use for the transmission of genetic material in intervarietal crosses are discussed. The producing of hybrids is shown to be an efficient method to obtain Actinomycetes strains with new properties. Properties of recombinants obtained in intervarietal crosses Streptomyces coelicolor A3(2)XS. lividans 66 are shown to possess new antibiotic properties differing from those of parental strains: they suppress a number of Actinomycetes and bacterial strains which are not affected by parental strains. It is found that at least two groups of genes located on chromosomes of S. coelicolor A3(2) and S. lividans 66 participate in the synthesis of the antibiotic. The obtaining of recombinants between S. coelicolor A3(2) and S. griseus 15 makes possible to select variants which are capable to produce the antibiotic grisine and are resistant to actinophages, specifically attacking S. griseus. Properties of recombinants between S. coelicolor A3(2) and S. griseus 15 make possible to localize on parental chromosomes regions containing genes which control the synthesis of the antibiotic, the formation of a receptor for the adsorption of actinophages, and genes controlling the restriction and t he modification of actinophage development in S. coelicolor and S. griseus. A sex plasmid (SGP1) is found in S. griseus 15.

Actinomyces↗

PubMed1975

[Characteristics of Actinomyces griseus actinophages and the production of phage-resistant mutants of the producer of grisin].

Analysis of phagolysates in production of fodder grisin provided determination of 3 serologically and morphologically different actinophages, 2 of which, i. e. Pg 81 and Pg 100 affected the sensitive culture as virulent phages and 1, i. e. Pg 2 affected it as a moderate phage. Investigation of the fermentation broth of strain 15 of Act. griseus did not confirm the supposition that this strain was polylysogenic and actinophages Pg 81 and Pg 100 were virulent mutants of moderate phages present in the cells. A phenomenon of limitation and modification controlled by the host cell was noted in the sensitive culture infected with actinophage Pg 81. The actinomycete mutants which did not limit but modified the phage were isolated. Under the effect of chemical mutagens the actinomycete mutants stable to virulent phages were selected. Treatment of the phage-stable mutants with ethylene imine and UV-light provided an increase in their antibiotic production levels by 75 to 80 per cent.

Anti-Bacterial Agents↗

PubMedDate not supplied

[Isolation of peptide antibiotic virginiamycin components and selection of their producer Streptomyces virginiae].

A method for chromatographic separation and quantitative determination of individual components of the antibiotic virginiamycin, produced by microbiological synthesis (Streptomyces virginiae strain 147), is described. The components, M1-2 and S1-5, were isolated from fermentation broth and identified by HPTLC and HPLC (the results obtained using the two methods correlate well with each other). Conditions of culturing of the producer and compositions of nutritive media were optimized. Using UV irradiation as a mutagenic factor, the producer was selected for increased level of synthesis of the antibiotic; this was achieved by inducing mutations that impart resistance to virginiamycin and meta-fluorophenylalanine, an analog of phenylalanine.

Anti-Bacterial Agents↗

PubMedDate not supplied

[Preparation of an active strain of Bacillus licheniformis--producer of thermostable alpha-amylase].

A highly potent strain of Bacillus licheniformis 103 that synthesized thermostable alpha-amylase with temperature and pH optima of 90-95 degrees C and 6.0-8.5, respectively, was obtained by mutagenesis and selection. The composition of fermentation media and conditions for submerged cultivation of the producer were optimized. alpha-Amylase whose activity reached 260 U/ml was obtained in laboratory fermenters.

Bacillus↗

PubMedDate not supplied

[Autoregulation of phenotypic dissiciation in Bacillus licheniformis].

Regulation of phenotypic variability of Bacillus licheniformis mediated by autoinducers of anabiosis, d1-factors was investigated. These factors are represented by alkylhydroxybenzenes. Colonial morphological variants of B. licheniformis were obtained and described (of R,S,M-types) in the first passage of both vegetative proliferative and resting cells. Resting cells were of different type, spores and cyst-like refractile cells induced by autoinducers of anabiosis. The possibility to manage the spectrum of dissociants by the mean of autoinducers of anabiosis was demonstrated.

Bacillus↗