Induction of transposon Tn1 translocations as affected by different mutagens

Transposition of ampicillin Tn1 transposon is repressed under normal conditions and occurs with low frequency (10(-4) per cell). Treatment of Escherichia coli cells with 22 c+mytomycin C, nitrosoguanidine and UV light induced transposition of Tn1 into different replicons. The degree of induction depended upon the strain of bacteria and the replicon which the transposon was inserted into. Mutation recA did not influence spontaneous translocation of the transposon but fully repressed induction of transposition during the period of mutagen treatment. In the present paper, the connection of inducible transposition process with the recA and lexA inducible functions of E. coli is discussed.     

Unfolding of tertiary structure ofHalobacterium halobium flagellins does not result in flagella destruction

The structure ofHalobacterium halobium R₁M₁ flagella is investigated by the methods of scanning microcalorimetry, circular dichroism, and electron microscopy. It is shown that melting curves of flagella in solutions with a different concentration of NaCl display only one peak of heat capacity that corresponds to one cooperatively melting domain. It is found that flagella do not dissociate after melting. The possible structural organization of archaebacterial flagella is discussed.     

Isolation and purification of restriction endonuclease BpeI from Bordetella pertussis

New restriction endonuclease has been isolated from Bordetella pertussis vaccine strain 305 and purified in 1 stage on Sepharose covalently bound with blue dextran. The isolated restrictase has been found capable of breaking down lambda-phag DNA into 7 fragments. According to its specificity, Bpe I is the isoschizomer of Hind III obtained from Haemophilus influenzae strain Rd.     

Change in the selection of microRNA strands during DNA damage induction

It was first shown that DNA damage induction in mitomycin C-treated HeLa cells leads to a change in the selection of 5p and 3p microRNA duplex strands in the formation of the RNA-induced silencing complex (RISC).     

Hormone-dependent insertional Arabidopsis thaliana mutants with decreased viability and fertility

We present data on the phenotype identification and genetic analysis of offspring in three lines of dominant morphological mutants of Arabidopsis thaliana having drastically reduced fertility (a sterile calluslike mutant, a flower mutant, and a dwarf mutant) and in five lines of recessive morphological mutants (four mutants with lethal seedlings and one pigmentation mutant). The mutants were selected from a collection of transgenic plants that had genomes carrying a T-DNA insertion of plasmid vectors pLD3 and pPCVRN4; the collection was created earlier via agrobacterial transformation of germinating seeds. The results presented here were obtained using compensation of hormonal imbalance in the insertional morphological mutants of A. thaliana by exogenous hormones.     

Microbiological Processes in a High-Temperature Oil Field

Thermophilic sulfate-reducing bacteria (SRB) oxidizing lactate, butyrate, and C₁₂–C₁₆ n-alkanes of oil at a temperature of 90°C were isolated from samples of water and oil originating from oil reservoirs of the White Tiger high-temperature oil field (Vietnam). At the same time, no thermophiles were detected in the injected seawater, which contained mesophilic microorganisms and was the site of low-temperature processes of sulfate reduction and methanogenesis. Thermophilic SRB were also found in samples of liquid taken from various engineering reservoirs used for oil storage, treatment, and transportation. These samples also contained mesophilic SRB, methanogens, aerobic oil-oxidizing bacteria, and heterotrophs. Rates of bacterial production of hydrogen sulfide varied from 0.11 to 2069.63 at 30°C and from 1.18 to 173.86 at 70°C g S/(l day); and those of methane production, varied from 58.4 to 100 629.8 nl CH₄/(l day) (at 30°C). The sulfur isotopic compositions of sulfates contained in reservoir waters and of hydrogen sulfide of the accompanying gas indicate that bacterial sulfate reduction might be effective in the depth of the oil field.     

Saving insertional recessive lethal mutants of Arabidopsis thaliana

A group of 13 recessive lethal mutants was selected on the basis of the collection of Arabidopsis thaliana transgenic plants with insertions of T-DNA vector plasmid pLD3 or pPCVRN4, which was produced by agrobacterial transformation of germinating seeds. The use of media containing exogenous hormones made it possible to compensate the lethal effect, identify phenotypes, and characterize six lines of recessive lethal germlings using genetic and molecular-genetic methods.     

Effectiveness of a battery of tests to assess the potential mutagenic danger of chemical compounds

A new method for assessing the efficiency of batteries of arbitrary numbers of tests is proposed. The posterior probability of the mutagenicity of the substances studied has been estimated using discriminant analysis. The results of tests in each test system has been presented as the probability to obtain a positive result in the given test system. This has made it possible to decrease the sample size as the number of tests in the battery increased. As a result, prognostic power may be assessed even if the matrix of results is incomplete. This approach has been used to estimate the weights of evidence for mutagenic activities of 105 chemical compounds studied by means of a battery of four tests: Ames's test, the test for chromosome aberrations in vitro, the test for cytogenetic defects in vivo, and the test for dominant lethal mutations in rodents.