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Biomedical subjects

S V Kameneva

Publications and source records attributed to S V Kameneva.

At least 19 recordsLinked to original sources
PubMed2001

[Cloning and identification of an Agrobacterium radiobacter 5D-1 chromosome fragment involved in control of nitrogen metabolism, biosynthesis of indolylacetic acid and replication of ColE1 plasmids].

Pleiotropic chromosomal mutations were earlier identified in saprophytic associative bacterium Agrobacterium radiobacter 5D-1. The mutations changed nitrogen metabolism, disturbed synthesis of indolylacetic acid (IAA), and conferred the ability to sustain replication of ColE1 plasmid derivatives, which are not normally maintained in bacteria other than Escherichia. The mutations were designated Nr (Nitrogen metabolism) and assigned to a single cluster on an A. radiobacter genetic map. A 420-bp fragment AGH23.1.1 was cloned from an agrobacterial genomic library. Introduced in the Nr mutants as a part of a pUC18-based recombinant plasmid, the AGH23.1.1 fragment complemented the Nr mutations with respect to nitrogen metabolism and IAA biosynthesis, but transformants still sustained replication of ColE1 plasmids. Transformation with the linear AGH23.1.1 fragment was due to substitution of a mutant allele of the nr gene with its wild-type counterpart as a result of recombination and completely restored the wild type in the Nr mutants, including the inability to maintain ColE1 plasmids. The AGH23.1.1 fragment and its flanking regions were sequenced. The established sequence was shown to contain two open reading frames (ORFs) coding for proteins with unknown functions. Thus, the cloned fragment contained a gene(s) that controls nitrogen metabolism and IAA synthesis and prevent replication of ColE1 plasmids in A. radiobacter cells. Possible variants of the genetic control of these processes are considered.

Cloning, Molecular↗
PubMed1999

[Genetic control of processes of bacterial interactions with plants in associations].

This review is devoted to the mechanisms and genetic control of processes underlying the formation and efficiency of associative relationships between bacteria and plants. The role of different polysaccharides and cellular fibrils in the appearance of associative relations and the biosynthetic pathway of these compounds and structures is considered. The molecular mechanisms of bacterial systems responsible for stimulating plant growth and development--nitrogen fixation and synthesis of a plant hormone, indoleacetic acid--are presented. The properties of associative bacteria are discussed in comparison with the relevant characteristics of the most studied free-living or symbiotic model species of bacteria.

Bacteria↗
PubMed1998

[Bacterial conjugative transposons].

Data on conjugative transposons of Gram-positive and Gram-negative bacteria are reviewed. Their organization and the mechanism of their transposition and mobilization of other replicons are considered. The transposition regulation by tetracycline and the role of conjugative transposons in bacterial gene transfer are briefly discussed.

Conjugation, Genetic↗
PubMed1988

[Mutants of the phototrophic bacteria Rhodobacter sphaeroides sensitive to the mutagenic action of long-wave ultraviolet light].

The mutagenic action of near ultraviolet (NUV, greater than or equal to 280) nm) on purple phototrophic soil bacteria Rhodobacter sphaeroides: wild strain 2R and 12 mutants obtained earlier sensitive to UV derivates (UVS) was investigated. The mutagenic action of NUV was measured by induction of resistance to tetracycline (Tet) and nalidixic acid (Nal) and reversion of pigment mutants to wild-type phenotype. The NUV light induces the mutations of resistance to Nal and Tet in wild-type strain 2R; the UVS mutants differed greatly in their NUV-induced mutability. Three UVS mutants were characterized by greatly increased mutability in all analysed loci; slight mutability was found in seven mutants. On the basis of the data obtained it has been concluded that the UVS mutants R. sphaeroides can be used as test organisms in estimation of mutagenic activity of NUV. The molecular mechanisms and genetic control of NUV-induced mutagenesis are discussed.

Drug Resistance, Microbial↗
PubMed1987

[Mobilization of the pACYC184 plasmid by hybrid pAS8-121 delta plasmids in Escherichia coli cells].

The plasmid pACYC184 is shown to be mobilized for conjugal transfer in Escherichia coli cells by the deleted (Tn7-TcR) derivatives of the hybrid conjugative plasmid pAS8-121 (RP4-Co1E1). Both the mobilized and mobilizing plasmids are autonomously inherited by the recipient cells when the mobilizing plasmid carries single copy of IS8 (the plasmid pAS8-121 delta 16). Cointegrates pAS8-121 delta 16D:: ::pACYC184 are found in the recipient cells with pACYC184 being inserted between two repeats of IS8 if the derivate plasmid pAS8-121 delta 16D having the duplication of IS8 is used to mobilize pACYC184 for conjugal transfer. The insertion of pACYC184 between IS8 repeats in the plasmid pAS8-121 delta 16D eliminates the plasmid ability to be inserted with high frequency into the chromosome of the phototrophic bacterium R. sphaeroides 2R. The cointegrate pAS8-121 delta 16D:: pACYC184 is stable but can be resolved during the transformation deriving the plasmid pACYC184:: IS8. The latter may be used as a probe for isolation and analysis of IS8 DNA sequences and for constructing the vectors on the basis of pACYC184.

DNA Transposable Elements↗
PubMed1985

[Variants of the plasmid pAS8 delta with increased frequency of integration into Rhodopseudomonas sphaeroides chromosome--the result of IS8-element duplication].

The possible participation of IS8 and IS elements of Rhodopseudomonas sphaeroides in cointegrate formation by chromosome of the purple bacterium and plasmid pAS8-121 delta has been studied. The plasmid derivatives having deleted Tn7 have been studied. Plasmid integration into the chromosome of the purple bacterium is shown to be mediated by IS8 element of the plasmid. Plasmid derivatives having the integration potential increased for two orders were isolated by a series of intergeneric conjugational crosses during which plasmid pAS8-121 delta was transferred from Rhodopseudomonas sphaeroides (cointegrate of plasmid and chromosome) to Escherichia coli (plasmid in an autonomous state) and back to Rhodopseudomonas sphaeroides. The restriction analysis of plasmid DNA digested by Hpal and Smal restriction endonucleases has revealed the tandem duplications of IS8 in plasmids capable of integration into the chromosome of the purple bacterium with a high frequency.

Chromosomes, Bacterial↗
PubMed1984

[Inheritance of hybrid plasmid pAS*-21 by cells of the purple phototropic nitrogen-fixing bacterium Rhodopseudomonas sphaeroides].

Clones of purple nitrogenfixing prototrophic bacterium Rhodopseudomonas sphaeroides carrying an incertion into the chromosome of the hybrid pAS8-121 (RP4-ColE1 (repA::Tn7] plasmid were analysed. It is revealed that plasmid integration could be due to both Tn7 and other migrating elements (IS8 and possibly, to resident migrating elements of purple bacteria). The plasmid pAS 8-121 can be autonomously transferred from the cointegrate state into Escherichia coli K-12; the plasmid is not inherited autonomously in cells of the purple bacterium. In E. coli cells R' derivatives of the plasmid carrying R. sphaeroides chromosomal fragments may be formed. The R' plasmids with fragments of plasmid DNA substituted for chromosomal material of R. sphaeroides were selected in E. coli K-12 cells among deleted (Kms) derivatives of pAS8-121.

Chromosomes, Bacterial↗
PubMed1983

[Lethal and mutagenic action of solar radiation on model microbiological test systems].

Lethal, mutagenic and recombonogenic action of the solar radiation on the model microorganisms--phage T4, bacteria Escherichia coli and ascomycet Aspergillus nidulans--has been studied. A considerable lethal effect of the solar radiation on phage T4 and E. coli was found. An increasing of mutation frequency in E. coli and A. nidulans by sunlight was also revealed. Recombinogenic action of solar radiation has been demonstrated in the experiments with diploid A. nidulans strains. It was shown that the excision and postreplication repair systems took part in recovery of damages induced by sunlight. An important role of ultra-violet region (280-320 nm) solar radiation in induction of lethal and mutagenic effects was demonstrated for all investigated microorganisms.

Aspergillus nidulans↗
PubMed1982

[Conjugation in Rhodopseudomonas sphaeroides mediated by R plasmids].

Plasmids R68.45, RP4, RP4::Mu cts62, RP1ts::Tn10, RP1ts::Tn9, Rts1 and RP41 were transferred into cells of photosynthetic nitrogen-fixation bacterium Rhodopseudomonas sphaeroides from Escherichia coli and Pseudomonas aeruginosa. The transfer of plasmids occurred with high frequency of 10(-1) to 10(-2) per donor cell in all cases. Mobilization of R. sphaeroides 2R chromosome was obtained by RP4 and Rts1 plasmids at a frequency of 10(-7) to 10(-8) per donor cell in all cases. Mobilization of R. sphaeroides 2R chromosome was obtained by RP4 and Rts1 plasmids at a frequency of 10(-7) to 10(-8) per donor cell. Bacteriophage Mu cts62 could be induced from the plasmid DNA in R. sphaeroides 2R cells and was capable of the lytic growth and producing phage progeny. It was demonstrated that an increase in the efficiency of donor chromosomal genes transfer into recipient cells could be achieved in crosses with the donor carrying RP4::Mcts62 plasmid.

Bacteriophage mu↗
PubMed1982

[Genetic control of recombination processes in Aspergillus nidulans. IV. The effect of uvs mutations on the frequency of spontaneous and nitrosomethylurea-induced intragenic mitotic recombination].

Effects of three uvs mutations were studied on spontaneous and nitrosomethyl-induced intragenic mitotic segregation in the methA region of the chromosome II in Aspergillus diploids homozygous for uvs and heteroallelic for methA mutation. The reversion frequencies of methA alleles in parent haploid strains were also determined. All the mutations increased the frequency of spontaneous and decreased that of induced intragenic mitotic recombination. The frequency of spontaneous reversions was decreased in uvs haploids. The interaction between repair, recombination and mutagenesis processes in Aspergillus nidulans is discussed.

Alleles↗
PubMed1980

[Mutagenic effect of combined exposure to 8-methoxypsoralen or angelicin and long-wave ultraviolet light in uvs-strains of Aspergillus nidulans].

Combined mutagenic effect of near ultraviolet irradiation (NUV, lambda > 320 nm) and angelicin, which forms monoadducts, or 8-methoxypsoralen (8-MOP), which forms monoadducts and cross-links in DNA, were studied in uvs and uvs+ strains of Aspergillus nidulans. Mutations were induced intensively by both kinds of furocumarins. The induction of mutations by angelicin testifies the significance of psoralen-pyrimidine monoadducts in mutagenesis. Using the method of fractionating NUV-irradiation and studying the influence of monoadducts repair to the mutation frequency, it is found the interstrand crosslinks of DNA induced by 8-MOP plus NUV are also nighly mutagenic. The products of genes uvs 12, uvs 20b and uvs 26, acting in DNA excision repair, do not participate in forming the mutations induced by furocumarins plus NUV in Aspergillus nidulans. The products of genes uvs 19, uvs 20a, participating in DNA post-replicative repair, are important for repair of premutational damages induced by furocumarins plus NUV.

Aspergillus nidulans↗
PubMed1979

[UV-induced DNA degradation in Aspergillus nidulans cells].

UV-induced DNA degradation was studied in mycellial cells of Aspergillus nidulans wild type and several uvs mutants. It was shown to be an enzymatic specific process which possibly reflects the excision of pyrimidine dimers from UV-damaged DNA. Inhibition of DNA degradation by caffeine and 2,4-dinitrophenol shows the connection between degradation and repair of DNA. Two ways of DNA degradation were found in A. nidulans cells, one of them being glucose dependent and the other--glucose independent. The dependence of DNA degradation on protein synthesis before and after UV-irradiation was demonstrated. The scheme of ways of DNA degradation and its genetic control were suggested on the basis of uvs mutations effect on UV-induced DNA degradation.

Amino Acids↗
PubMed1978

[Isolation and genetic study of Aspergillus nidulans mutants defective in pyrimidine biosynthesis].

8 uridine-requiring pyr mutants were isolated from Aspergillus nidulans under nitrosoguanidine treatment. All the mutants are capable to grow on the medium containing 20 mkg/ml of uridine or cytidine, or 100 mkg/ml of uracil, and they do not utilize thymidine, thymine, cytosine and deoxyuridine. Their ability to grow in the presence of orotic acid demonstrates that the pyrimidine synthesis in all the mutants is blocked at stages preceding the conversion of orotic acid into orotidine monophosphate. All the pyr mutants are of nuclear nature, they are recessive and represent three complementation groups located in the VIII chromosome. Unlike U. maydis mutant, the requirement in pyrimidines does not increase the sensitivity of A. nidulans pyr mutants to UV-irradiation.

Aspergillus nidulans↗
PubMed1977

[Genetic control of the sensitivity of Aspergillus nidulans to mutagenic factors. VII. Inheritance of cross-sensitivity to different mutagenic factors by uvs-mutants].

To study the inheritance of the sensitivity to UV, X-rays, methylmethanesulphonate (MMS), nitrosoguanidine (NG) and nitrous acid (NA) in five uvs mutants of Aspergillus nidulans, having multiple sensitivity to these factors, the sensitivity of recombinants obtained from crossing uvs mutants with uvs+ strain, resistant to all the factors analysed, and uvs leads to uvs+ revertants is investigated. Four uvs mutants (15, 17, 19 and 26) are found to have a nomogenic control of sensitivity to different mutagens. In one mutant (uvs11) the sensitivity to five factors is controlled by two non-linked mutations, one of them determining the sensitivity to UV, NG, NA, and the other--to X-rays and MMC. Phenotypic manifestations of uvs mutations is modified by cell genotype, both chromosomal and cytoplasmic factors being responsible for the modification. Phenotypic modification of uvs mutation results in the change to some (but not to all) mutagenic factors. It suggests, that not the product of uvs gene, but some other components of the reparation complex are modified. Otherwise, reparation of different DNA damages can be carried out by a single enzyme acting in different reparation complexes.

Aspergillus nidulans↗