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N D Lomovskaia

Publications and source records attributed to N D Lomovskaia.

At least 19 recordsLinked to original sources
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↗
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

[Cloning of grisin resistance gene gsr and the study of its functioning in Streptomyces griseus Kr. strain].

S. griseus Kr. is a commercial strain producing grisin, an antibiotic of the streptothricin group used as a feed additive. It was shown earlier that genetic instability of the strain was very high which was evident from a high frequency of nonreverting Grn- Grns mutants. With densitographic analysis of chromosomal DNA electrophoregrams and DNA-DNA hybridization it was revealed that the molecular basis of the genetic instability of the S. griseus strain was deletion of a DNA fragment about 20 kb in size containing a grisin resistance gene. The resistance gene designated as gsr was cloned to S. lividans TK 64 within the plasmid vector pIJ699. The restriction map of a cloned DNA fragment with a gsr gene was constructed and its similarity to that of a nat gene resistant to norseothricin, another streptothricin was observed. Introduction of a gsr gene within the multicopy plasmid pIJ699 into S. griseus 212, a highly productive strain synthesiing the antibiotic, led to an increase in its resistance and productivity. Proceeding from the preliminary data on possible linkage of a gsr gene and grisin biosynthesis genes, it appeared possible to use the cloned gene as a molecular probe in cloning the biosynthesis genes.

Anti-Bacterial Agents↗
PubMed1990

[Molecular cloning of chlortetracycline resistance gene from chlortetracycline producer Streptomyces aureofaciens].

The chlortetracycline (CT) resistance gene ctr was cloned from S. aureofaciens 633, a strain producing the antibiotic. The 6.6-kb DNA Bam HI fragment containing the resistance gene was cloned with the plasmid vector pIJ699. Comparison of the restriction maps of the cloned gene and the oxytetracycline (OT) resistance gene otrA from S. rimosus revealed their similarity which enabled identification of the cloned resistance gene as otrA. Investigation of the resistance determinants in S. aureofaciens 633 made it possible to identify a mtr gene(s). It was demonstrated that introduction of a ctrA gene into S. lividance provided a simultaneous increase in the resistance of the recipient strain to CT and a number of macrolide antibiotics. The CT resistance determinants in S. lividans TK64 showed properties of exogenous induction by CT and the macrolide antibiotics similar to the properties of the mtr gene(s) of S. aureofaciens. Possible adaptation properties of mtr genes are discussed.

Chlortetracycline↗
PubMed1989

[Characterization of multiple changes of antibiotic resistance characters in Streptomyces coelicolor A3(2)].

Among mutants of Streptomyces coelicolor A3(2) studied which were sensitive to chloramphenicol (Cmls), strains sensitive to a number of antibiotics (ristomycin, tetracycline, polymyxin, lincomycin) amount of 46%. Antibiotic-sensitive mutants are capable to form different classes of resistant revertants with frequency varying from 10(-2) to 10(-6) in independent strains. Ristomycin-sensitive clones (Rims) have been found to occur with high frequency in Cmls strains and Cmlr revertants. Mutations mediating the Rims phenotype are mapped in a locus linked to the gene for resistance to chloramphenicol. The results obtained are discussed, in accordance with the notion about possible role of cml mutation in induction of secondary mutational changes in the genome of S. coelicolor A3(2).

Chloramphenicol Resistance↗
PubMed1988

[Selection of strains of Streptomyces griseus Kr., the producer of a streptothricin antibiotic grisin, using the method of protoplast fusion].

The effect of protoplasting on antibiotic activity of the grisin-producing organism was shown. High frequency of Grn- mutants after strain VG307f protoplasting and no capacity in these mutants for reversion to the initial Grn+ phenotype were shown. The reversion frequency was less than 10(-8). Moreover, it was shown that all the Grn- mutants lost their stability (GrnR) to the effect of their own antibiotic. With respect to strain VG212 there was noted a significant increase in the number of both the minus and the plus variants after the protoplast formation and regeneration. Fusing of protoplasts of strains VG307f and VG212 belonging to the divergent lines in selection of S. griseus Kr. yielded the phage stable strain VG7849 with high levels of the antibiotic production and improved technological properties.

Anti-Bacterial Agents↗
PubMed1988

[Genetic mapping of unstable chloramphenicol resistance determinant in Streptomyces coelicolor A3(2)].

The results indicative of chromosomal localization of the unstable chloramphenicol resistance determinant in Streptomyces coelicolor A3(2) have been obtained. Independent mutations specifying chloramphenicol sensitivity in different strains of S. coelicolor A3(2), S18 and A617M are localized in the same region flanked by markers argA1 and cysD18 on the genetic map. Mutations restoring chloramphenicol resistance are also localized in this region. Different locations of the genetically unstable determinant of chloramphenicol resistance detected in various laboratories are discussed, in relation to the results showing that transfer to chloramphenicol sensitivity is due to a set of various rearrangements (deletions, amplifications, deamplifications, etc.), differing in separate variants.

Chloramphenicol Resistance↗
PubMed1987

[Molecular cloning and study of the expression of a region of a diphtheria toxin gene encoding fragment A of the Streptomyces lividans 66 strain].

The shuttle plasmid pVG202 containing a part of diphtheria toxin gene coding for fragment A has been constructed. S. lividans strain 66 has been transformed by the plasmid pVG202 DNA. The presence of the hybrid plasmid in S. lividans 66 cells determines the production of catalytically active toxoid secreted into the cultural liquid medium. The deleted plasmid pVG205 which determines for the increased catalytic activity has been selected and shown to be stably inherited by the bacterial cells.

Cloning, Molecular↗
PubMed1986

[Actinomycetes--the test-organisms of genetic engineering].

The paper contains a short review of the data on using the methods of genetic engineering in studies of genetics and molecular biology in Streptomyces. The techniques of DNA introduction into actinomycetes and wide-spread vectors are briefly described. The origin of the actinomycete plasmids as chromosomal segments capable of autonomous replication is discussed. In this view, it is suggested that genetic instability in actinomycetes is connected with excision of specific DNA sequences from the chromosome at frequencies characteristic of recombination events. Also, amplification of short DNA segments within the chromosome resulting in tandem repeats is a consequence of unequal crossing over between direct repeats flanking the amplifying DNA and, possibly, of induction of replication of this DNA. The data on molecular cloning of actinomycete genes for primary metabolism and those for resistance to and biosynthesis of antibiotics, on using actinomycetes as the hosts for foreign genes to be expressed, as well as on analysis of nucleotide sequences of actinomycete DNA, are presented.

Actinomycetaceae↗
PubMed1985

[Genetic control of Actinomycetes resistance to antibiotics].

The results of studies on genetic control of resistance to antibiotics in Streptomyces strains are discussed. Cloning and sequence analysis of resistance genes yield information concerning their expression in homo- and heterologous systems, allow analysis of signal sequences responsible for initiation of transcription and translation. Cloning of genes coding for resistance to neomycin,viomycin, thiostrepton in Streptomyces and Bac. licheniformis ermD gene made them convenient selective markers for constructing vector molecules, useful for identification of homology regions in S. fradiae aph gene and TnS of E. coli; the site homologous to ermD gene has been thus revealed in S. erythreus chromosome. Possibilities of the studies aimed at elucidation of instability of many actinomycete characters using determinants of natural multiple resistance to antibiotics as a model are demonstrated. It has been shown that genetic instability is not related to the loss of plasmids and is associated with genes having chromosomal location. Simultaneous high frequency loss of a number of resistance characters determined by non-linked genes suggests the participation in gene activity regulation of actinomycete genome rearrangements. This is confirmed by evidence for such rearrangements found in strains with mutant phenotypes, including deletions in tyrosinase and streptomycin phosphotransferase genes in Mel- and StrS strains of S. reticuli and S. glaucescens.

Actinomycetaceae↗
PubMed1982

[Genetic characteristics of a new phage resistance trait in Streptomyces coelicolor A3(2)].

Phage resistance was investigated in the system of Streptomyces coelicolor A3(2) and phi C31 actinophage. Resistance of A3(2) strain to phi C31 was shown to involve a novel mechanism responsible for the arrest of phage intracellular growth in the whole cell population. The phage resistance character designated Pgl+ (for "phage growth limiting") is determined by a gene located on the A3(2) chromosome. The gene (pgl) controls phage "modification" which results in an inability of phage to lyse lysogenize Pgl+ host. Instability of the Pgl+ character was revealed. Pgl+ strains segregate Pgl variants at a high frequency, the majority of Pgl strains reverting to the initial Pgl+ phenotype with the same high frequency. Reversible Pgl+ in equilibrium Pgl transitions are a common feature of A3(2) cell population.

Bacteriophages↗
PubMed1981

[Genetic mapping and characteristics of the actinophage phi C31 deletion mutants of Streptomyces coelicolor A3(2) incapable of lysogenization].

Actinophage phi C31 deletion c mutants with impaired ability to make repressor were genetically studied. Genetic crosses indicate that the c28 deletion mutant is situated with the c-region of the phi C31 genetic map. Based on the results of a qualitive test for recombination between several c mutants, a scheme of their order relative to deletion mutants was presented. The approximate distances between eight c mutants have been represented in units of the physical DNA map estimation. Genetic studies of actinophage lyg deletion mutants which cannot lysogenize sensitive cultures were carried out. Mutants failed to lysogenize upon mixed infection with lyg+ phages. The absence of the effect of lyg+ gene in trans suggests that lyg deletions cause a structural defect in an integration site of the phage. Preliminary data on alignment of lyg positions on physical and genetic maps of phi C31 phage have been obtained. According to evidence from genetic crosses, lyg mutation has been located in the right half of the phi C31 genome.

Bacteriophages↗
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↗
PubMed1981

[Plasmid SCP2 transfer by Streptomyces coelicolor A3(2) actinophages].

The ability of VP5 and phi c31 actinophages of Streptomyces coelicolor A3(2) to transfer plasmid SCP2 genes was tested. Infection with both phages led to formation of variants having the traits characteristics of plasmid bearing strains. The fertility properties of the variants suggested the presence of SCP2 in the autonomous state. Analysis of extrachromosomal DNA isolated from these variants demonstrated its identity with the plasmid DNA from the donor strain. Based on characteristics of the variants obtained, it was suggested that the whole SCP2 plasmid had been transferred by actinophages via general transduction.

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↗
PubMed1979

[Determination of Streptomyces coelicolor A3(2) resistance to erythromycin].

Resistance to erythromycin is genetically unstable in strains of Streptomyces coelicolor A3(2). The frequent loss of resistance as well as reversion of sensitive variants to the original unstable resistance phenotype excluded the possibility that plasmid elimination is involved. The spontaneous frequency of occurrence of sensitive clones was 0.14 to 1.5%, the rate of reversion ranging from 1.10(-6) to 1.10(-8). Resistance to erythromycin has been mapped on the chromosomes of two S. coelicolor A3(2) derivatives in different sites: between markers adeC (v 10) and ArgA1 in the strain A617, between pheA1 and SCP1 in the strain S18. It is suggested that genetic instability of erythromycin resistance determinants having chromosomal location is due to transposition of genetic material.

Drug Resistance, Microbial↗