[Effect of He-Ne-laser irradiation on plasmid transformation of Escherichia coli bacteria]. / Vliianie izlucheniia He-Ne-lazera na plazmidnuiu transformatsiiu bakterii Escherichia coli.

The influence of the of radiation a He-Ne laser (632.8 nm, 30 W/m2, 5-20 J/m2) on the transformation of Escherichia coli cells with plasmid DNA was studied. The irradiation of a mixture of bacterial cells and plasmid DNA increased the transformation efficiency 2.5-3 times, thus offering an alternative to the heat treatment commonly used. In contrast to the standard techniques, the laser-induced increase in the transformation efficiency was accompanied by a 1.7- to 2-fold increase in cell survival. The effect of the 632.8-nm light, know to be absorbed by membrane porphyrin components, is supposed to be mediated via a modification in the replication and transformation DNA-membrane complexes in E. coli cells.

[Lethal and mutagenic action of solar radiation on model microbiological test systems]. / Letal'noe i mutagennoe deistvie solnechnoi radiatsii na model'nye mikrobiologicheskie test-sistemy.

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.

In vitro repair of UV-or x-irradiated bacteriophage T4 DNA by extract from blue-green alga Anacystis nidulans.

The cell-free extract from blue-green alga Anacystis nidulans contains enzymatic activities which repair in vitro transforming DNA of bacteriophage T4 damaged by UV light or X-rays. The repair effect of the extract was observed with double-stranded irradiated DNA but not with denatured irradiated DNA. The level of restoration of the transforming activity depends on the protein concentration in the reaction mixture and on the dose of irradiation. A fraction of DNA lesions induced by X-rays is repaired by a NAD-dependent polynucleotide ligase present in the extract. The repair of UV-induced lesions is the most efficient in the presence of magnesium ions, NAD, ATP and the four deoxynucleoside triphosphates. The results indicate that the repair of UV-irradiated DNA is performed with the participation of DNA polymerase and polynucleotide ligase which function in the cell-free extract of the algae on the background of a low deoxyribonuclease activity.