RESUMO
The factors potentiating the efficacy of fusion of protoplasts of Bacillus subtilis were studied. A 50-fold increase in the yield of primary prototrophs was provided by 90-minute preincubation of protoplasts in a liquid hyperbaric medium and 10-minute treatment with trypsin. Increased efficacy of fusion of protoplasts depended on their regeneration percentage.
Assuntos
Bacillus subtilis/genética , Protoplastos/fisiologia , Aminoácidos/farmacologia , Bacillus subtilis/efeitos dos fármacos , Hibridização Genética , Soluções Hipertônicas , Protoplastos/efeitos dos fármacos , Tripsina/farmacologiaRESUMO
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. The most sensitive were the cells defective in DNA polymerase I. The optimal conditions for DNA repair in the strains under investigation were established. 90% of MNU-induced SS are repaired by DNA polymerase I and do not depend on protein synthesis. On the other hand, the exrA and recA dependent ways of SS repair depend on protein synthesis. The existence of an inducible recAexrA-dependent repair system of NMU-induced lesions in bacterial DNA is proposed.
Assuntos
Reparo do DNA/efeitos dos fármacos , DNA Bacteriano/genética , DNA de Cadeia Simples/genética , Genes/efeitos dos fármacos , Metilnitrosoureia/farmacologia , Mutação/efeitos dos fármacos , Compostos de Nitrosoureia/farmacologia , Relação Dose-Resposta a Droga , Escherichia coli/efeitos dos fármacos , Escherichia coli/genética , GenótipoAssuntos
4-Nitroquinolina-1-Óxido/toxicidade , Mutagênicos/toxicidade , Nitroquinolinas/toxicidade , Plasmídeos , Salmonella/genética , Raios Ultravioleta , DNA Bacteriano/genética , Escherichia coli/genética , Peso Molecular , Salmonella/efeitos dos fármacos , Salmonella/efeitos da radiação , Salmonella typhimurium/genética , Especificidade da EspécieRESUMO
The survival of Salmonella typhimurium wild type strains after UV-irradiation is studied. It is demonstrated that many of these are more sensitive to UV-irradiation than Escherichia coli of the wild type. Alkaline sucrose density gradient centrifugation has demonstrated a deficiency of these strains in normal excision repair of UV-damaged DNA. This deficiency is not a feature of Salmonella genus, because a strain is found of the same resistance and reparation ability as E. coli wild type strain.
Assuntos
Reparo do DNA/efeitos da radiação , DNA Bacteriano/efeitos da radiação , Salmonella typhimurium/efeitos da radiação , Raios Ultravioleta , Escherichia coli/efeitos da radiação , Mutação/efeitos da radiaçãoRESUMO
The Escherichia coli structural gene for DNA polymerase I was inserted into Salmonella typhimurium chromosome by conjugal transfer. The genetic analysis of P1-mediated transduction of obtained hybrid showed that polA gene is located in it between metE and rha loci and is cotransduced with metE (about 50%) and rha (12%). The phenotypic properties of polA1 hybrid E. coliXS. typhimurium concerning UV-MMS-NG and gamma-ray sensitivity are similar to the polA1 mutants of E. coli.
