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Biomedical subjects

A G Skavronskaia

Publications and source records attributed to A G Skavronskaia.

At least 19 recordsLinked to original sources
PubMed2003

[Effects of plasmid pKM101 on the expression of Escherichia coli and Salmonella typhimurium genes under ultraviolet irradiation].

The study focused on plasmid pKM101, which is a necessary component of the short-term test of Eim's system (Salmonella-microsome test), to detect the potential carcinogens through their mutagen activity. We found a previously unknown feature of the plasmid to enhance the expression of certain plasmid and chromosome genes. The purpose of the present study was to examine and specify the role of operon mucAB responsible for the mutation properties of the plasmid in activating the expression of bacterial genes. An ultraviolet-induction examination of bacterial genes, with the mutants of plasmid pKM101 affecting operon mucAB being used, showed that the function of genes mucAB did activate, but, on the contrary, suppressed the induction of genes elt (i.e. of genes controlling the formation of LT-toxin of Escherichia coli) and of sfiA (SOS-regulated gen E. col controlling the cell division.

Bacterial Toxins↗
PubMed2000

[Use of molecular-biological methods for identifying brucella in a comparative analysis of strains, isolated from sick dogs].

Ten strains isolated from sick dogs in 1998 in St. Petersburg were studied by traditional and molecular biological methods of Brucella identification. PCR study confirmed that the isolated cultures were Brucellae, and comparative study of the traditional phenotypical characteristics and protein and antigenic composition allowed referring all the isolated strains to B. canis. Traditional identification showed similarity of 7 strains with the reference B. canis strain RM6/66, and 3 strains were similar to B. canis Mex 51 strain. These results confirmed the division of B. canis into two biovars. Polyacrylamide gel electrophoresis with sodium dodecyl sulfate demonstrated the identity of protein profiles of 10 strains isolated from dogs to the reference B. canis RM6/66 strain. Immunoblotting analysis with S- and R-specific rabbit antisera also demonstrated the identity of antigens binding IgG antibodies in the strains isolated from dogs to the reference B. canis RM6/66 strain.

Animals↗
PubMed1999

[Sensitivity and adaptation of various Brucella species to acid shock].

The sensitivity to acid shock (pH 2.5, 2.8, 3.0, and 3.3) and the capacity to adaptive acid tolerance response (ATR) is studied in the reference Brucella strains differing by the origin, biological, and virulent properties. The ability of Brucella to survive under conditions of acid pH depended on the medium composition, growth phase, and preliminary adaptation at pH 5.6. B. suis biovar 1 and B. melitensis biovar 3 were more resistant to low pH than other Brucella species. Adaptation by overnight growth at pH 5.6 (stationary phase) induced ATR to the acid shock (pH 3.3-3.0) in all Brucella species except B. abortus biovar 1. ATR induced in B. melitensis biovar 2, B. canis, and B. neotomae was more marked, with more than an 100-fold increase in survival of adapted cultures, while adapted B. suis biovar 1, B. melitensis biovars 1 and 2 showed a 2-24-fold increase in survival rates. The detected differences in acid sensitivity and ATR of various Brucella species may be useful for identification and characterization of Brucella strains.

Adaptation, Physiological↗
PubMed1999

[Increased production of the protein antigen of Brucella melitensis in Escherichia coli K-12 cells].

The production of Brucella melitensis protein antigen with molecular weight of 38 kD in Escherichia coli K-12 cell lysates has been studied by immunoblotting with various antisera. E. coli strains differed by the vector plasmid and the size of B. melitensis 565 DNA fragment with 38 kD protein gene, cloned in this plasmid. The immunoblotting analysis detected increased production of 38 kD protein in the recombinant GSE830 strain in comparison with the B. melitensis strain 565, from which the gene was cloned, and other E. coli strains containing this protein gene. The production of 38 kD protein was determined by the size of the cloned B. melitensis 565 DNA fragment with this protein gene, but not by the conditions of culturing.

Antigens, Bacterial↗
PubMed1998

[Comparative analysis of antigens from different Brucella species using immunoblotting with antisera from immunized rabbits].

Brucella antigens recognized by IgG antibodies in cell lysates from various Brucella species differing by the origin, biological, and virulent properties (including the reference, vaccine, and newly isolated strains) were compared by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Proteins in SDS-cell lysates were separated by 12% SDS-PAGE and protein gels were stained with Coomassie brilliant blue R-250 and Silver reagent. SDS-PAGE showed differences in the protein profiles of 15 strains of different species. Immunoblotting revealed that rabbit S-antisera contained IgG reacting with S-LPS and identical proteins of 90 to 16 kDa belonging to B, melitensis, B. suis, B. abortus, and B. neotomae strains. B. canis strains had 4 antigens reacting with these antisera, whereas B. ovis had none. No agglutinating antibody were detected by the standard tube agglutination test with smooth Brucella strains in rabbit R-antisera. By contrast, immunoblotting analysis with these sera demonstrated common 90-16 kDa antigens in the strains of B. melitensis, B. suis, B. abortus, B. neotomae, and B. canis. B. ovis possessed none of these antigens. These results confirm that all Brucella species except B. ovis possess common protein antigens reacting with IgG.

Animals↗
PubMed1997

[Relationship between the UV-induction of exact exclusion of transposons and the function of umuDC, lexA, recA genes and plasmid pkM101].

A pair of isogenic strains-E. coli K-12 and E. coli B/r differing by the status of umuDC genes and presence of pKM101 plasmid-were constructed and the relationship between UV induction of transposons Tn5 and Tn 10 and the gene umuDC function shown. This relationship is not absolute, in contrast to that of point mutations. Induction of precise excision of these transposons can be inhibited by pKM101 plasmid. Induction of precise excision of Tn5 and Tn 10 from the sites under study is absolutely lexA- and recA- dependent.

DNA Transposable Elements↗
PubMed1997

[Comparative study of the antigenic composition of Brucella canis strains by immunoblotting].

Brucella cultures isolated from sick dogs have not been properly studied in Russia up to the present time. In 1994 a culture has been isolated from aborted fetus of a dog. Investigations by the traditional methods referred it to Brucella genus, species canis (strain K-01). Reference strain B. canis RM6/66 and B. canis K-01 were identical by the profiles of protein antigens in immunoblotting with a set of antibrucellosis sera. B. canis, B. suis, B. abortus, and B. melitensis. However, immunoblotting with sera to B. canis showed the similarity of B. canis cultures with the reference strain B. suis 1330, and use of sera to B. suis, B. abortus, and B. melitensis helped differentiate between the reference B. suis 1330 strain and B. canis strains. All the antisera used permitted the differentiation of Brucella strains from Yersinia enterocolitica 0:9, Escherichia coli 0:157, and Salmonella typhimurium cross reacting with Brucella in serological tests. Immunoblotting is a promising taxonomic criterion for identification of newly detected representatives of the Brucella genus.

Animals↗
PubMed1994

[UV-induction of the LT-toxin operon depending on genes lexA, recA, and umuD].

UV induction of the elt operon (the LT-toxin operon in Escherichia coli) was demonstrated in experiments using fusion of elt::lac operons with the help of Mud1(Ap lac) phage. UV induction of the elt operon is lexA-dependent; thus, the possibility of SOS regulation of this process may be assumed. However, UV induction of the elt operon turned out to be recA-independent, which makes it impossible to consider this induction as a typical SOS response. UV induction of the elt operon is also observed in Salmonella typhimurium, which differs from E. coli in the product of umuD, which suggests that the UV induction of the elt operon is umuD independent.

Bacterial Proteins↗
PubMed1992

[Mutations in Francisella tularensis, decreasing the virulence of these bacteria and leading to a change in the immune response upon infection of experimental animals with them].

The research was aimed at isolation of Francisella tularensis mutants possessing the decreased virulence for experimental animals and mediating the changes in the animal immune response. A number of spontaneous and induced mutants of the American and European subtypes of Francisella tularensis were selected for antibiotics resistance or detergent sensitivity. All the obtained mutants have the decreased virulence and differ in their ability to induce the protective antitularemia immunity or ability to induce the humoral immune response in the laboratory animals. The dimeric immunoprecipitation in gel as well as immunoblotting have shown the mutations decreasing the virulence to cause the loss by bacteria of a number of antigenic structures (in case the virulence is completely lost) or changes in antigenic structure resulting in inability of bacteria to induce the humoral immune response when immunizing the laboratory animals. The latter occurs in partially virulent mutants of the vaccine mutant type. The concomitant changes in virulence, ability to cause protective immunity or humoral immune response of the mutants is discussed.

Animals↗
PubMed1991

[The possibility of creating a vaccinal strain of Brucella abortus 19-BA with multiple antibiotic resistance].

The possibility of preparing B. abortus vaccine strain 19-BA with multiresistance to antibiotics was shown. The strain was obtained by the spontaneous induction of resistance to rifampicin with the subsequent transformation of nonconjugative hybrid plasmid pOVI which, in addition to rifampicin resistance, governed the resistance of brucellae to tetracycline, doxycycline, ampicillin, and streptomycin. Experiments on guinea pigs demonstrated the immunization with both multiresistant vaccine strain GSA1 and B. abortus initial vaccine strain 19-BA.

Animals↗
PubMed1990

[Cloning of Brucella genes in Escherichia coli K12 cells and analysis of products of the cloned genes].

The libraries of Brucella melitensis 565 and Brucella abortus 99 in Escherichia coli cells have been constructed. Some clones of Escherichia coli producing the specific brucella antigens have been found in immunological tests with brucella antiserum. Two strains producing antigens have been characterized, one being from Brucella melitensis 565 and another from Brucella abortus 99 clone libraries . Both strains synthesize two antigens that were studied by immunoelectrophoresis, immunoblotting after treatment of antigen preparations with different physical and chemical agents substrate specific enzymes. Both strains are found to synthesize the specific brucella antigens of protein nature. One of them has the mol mass about 15 kD, another--31-32 kD. The 31-32 kD antigen can be, evidently, referred to as the main protein of an outer membrane of brucella.

Antigens, Bacterial↗
PubMed1990

[Construction and analysis of the tularemia pathogen gene library in Escherichia coli].

The library of tularemia causative agent genes cloned on the pHC79 plasmid and the partial clonotek of these agents genes in Escherichia coli cells have been constructed. The immunochemical analysis has revealed seven clones of Escherichia coli harbouring the recombinant plasmids and expressing francisella antigens. The cloned sequences of francisella DNA as well as the recombinant plasmids containing them and coding for francisella antigens are capable of specific hybridization with the DNA from Francisella tularensis strains and Francisella novicida strain U112. The cloned DNA sequences have the properties of the genetic radiospecific molecular DNA probe.

Blotting, Southern↗
PubMed1990

[Functional properties of the pOV13 plasmid as a vector for DNA cloning in a broad spectrum of gram negative bacteria].

The birepliconed plasmid pOV13 possesses all the properties of a vector for DNA cloning in a broad host range of bacterial cells. pOV13 is transfered by transformation and stably inherited by Escherichia coli, Brucella, Pseudomonas cells determining the resistance to streptomycin, tetrocycline and kanamycin in these bacteria. The plasmid pOV13 is a multicopy plasmid optimal in replication capacity (23kb). The plasmid carries single sites for some restriction endonucleases that are used for DNA cloning, including some restriction sites in antibiotic resistance genes. The examples of DNA cloning with the selection of recombinant clones by the insertional inactivation of kanamycin or tetracycline resistance and expression of the cloned DNAs are presented.

Cloning, Molecular↗
PubMed1989

[UV-inducibility of the LT-toxin operon].

The plasmid elt-operon pVZ14 was constructed by fusing of the eltoperon of the plasmid pVZ357 with the lac-gene of the bacteriophage Mud1 (Amp, Lac). lacZ gene has been proven to be fused with an elt-promoter by the loss of toxin production coded by pVZ357 and acquiring of Lac+ phenotype by pVZ14 containing cells, as well as by HindIII fragments hybridization of pVZ357 and pVZ14 with the labelled elt-probe. The kinetics of beta-galactosidase synthesis in E. coli cells harboring pVZ14 shows an elt-operon promoter to have expressed constitutive activity and to be activated by a SOS-inducing agent, UV-light.

Autoradiography↗
PubMed1989

[Isolation and characteristics of a recombinant pOV13 plasmid as a vector for DNA cloning in a broad range of bacterial hosts].

The hybrid plasmid pOV13 proposed as a potential vector for DNA cloning in a broad bacterial host range has been constructed on the basis of the broad host range plasmid RSF1010 and a shortened derivative of RP4, the plasmid pVZ115 serving a marker DNA fragment. The plasmid pOV13 contains the genes for streptomycin, kanamycin and tetracycline resistance and single cleavage sites for restriction endonucleases BamHI, BgIII, SalI, SmaI, PvuII, XhoI, as well as double cleavage sites for restriction endonucleases PstI and HindIII permitting one to clone DNA with insertional inactivation of genes. The physicogenetical map of the birepliconed plasmid pOV13 is presented.

Cloning, Molecular↗
PubMed1988

[SOS-induction of the RP4 plasmid tet-determinant].

Induction of the tetracycline-resistance genes function by the inducer of the DNA-repair and mutability SOS-system, UV-light, has been tested. Activity of the tet-genes residing on the plasmid RP4 in Escherichia coli cells has been shown to be inducible by the low doses of tetracycline as well as by the mutagenic doses of UV-light. The induction was quantitatively registered by measuring the activity of beta-galactosidase of bacteriophage Mud1 (Ap, Lac) inserted into the tet-genes of the plasmid RP4. The bacteriophage integration inactivates the tet-genes function of the constructed plasmid fusing the lac-operon to a promoter of inactivated genes. Precise excision of bacteriophage restores the activity of the tet-genes proving together with the plasmid DNA-restriction analysis the fusion of tet-promoter with Iac-operon. The tet-genes of RP4 are concluded to be a part of the SOS-regulon, a set of genes inducible by the conditions harming the bacterial cell. Preliminary data on the mutagenic activity of tetracycline obtained in the bacterial test-system of mutagens are discussed.

DNA Repair↗
PubMed1988

[Structural rearrangements of the plasmid R68,45 in cells of Brucella suis].

The mobilizing activity of the plasmid R68,45 in Escherichia coli and Brucella abortus has been studied. The plasmid R68,45 has been found to lose its ability to mobilize the chromosome in Brucella suis cells. The experiments on the conjugational transfer of R68,45 were confirmed by restriction analysis of the plasmid DNA. R68,45 has been shown to lose Cma in brucella cells via deletion. The molecular mechanisms of deletion process in brucella and other bacteria are discussed.

Brucella↗