[Selective effect of p-aminobenzoic acid on mutagenesis: phenotypic analysis of the Arg+-revertants induced by N-nitroso-N-methylurea in the Escherichia coli K-12 AB1157 strain].

According to the phenotypic analysis of Arg+ revertants in Escherichia coli K-12 AB1157, the specific mutational changes in bacterial cells under the action of MNU were registered. True and suppressor mutations of four phenotypic groups were noted. The quantity of mutants induced depended upon the DNA and protein syntheses in bacterial cells.

[Para-aminobenzoic acid intensification of DNA repair processes in Escherichia coli K-12].

Studies of the role of physiologically active natural compound, para-aminobenzoic acid (PABA) in genetic processes showed that PABA interacts with bacterial DNA and strongly increases the effectiveness of repair processes under the mutagenic action of NMU, NEU, MMS and EMS. These properties of PABA differentially depended on the activity of enzymatic systems fo DNA repair and were most pronounced in repair-proficient strains of Escherichia coli. For example, the cooperative action of E.

[Effect of B polA1- exrA- and recA-gene mutations on the reparation of single-strand DNA breaks induced by N-nitrosomethylurea].

The effect of different doses of N-methyl-N-nitrosourea (MNU) on a viability of bacterial cells with different defects in the systems of repair of UV-damages, and the MNU induction of single-strand DNA breaks (SS) were studied. The kinetics of both processes was investigated. There was a good correlation between the NMU sensitivity of bacterial cells and the number of SS in their DNAs.