RESUMO
Conventional mutagenesis (UV irradiation and exposure to nitrosoguanidine) were used to produce and regenerate protoplasts, aiming at increasing the antibiotic activity of a Streptomycesfradiae strain producing tylosin. Variants exceeding the activity of the initial producer strain by 0.5-28.3% were obtained. The most active variants were produced by a combined exposure to UV and nitrosoguanidine, as well as upon regeneration of protoplasts formed from the cells of clones produced by UV irradiation. Unstable inheritance of the trait of increased tylosin production was demonstrated.
Assuntos
Streptomyces/metabolismo , Tilosina/biossíntese , Mutagênese , Nitrosoguanidinas/farmacologia , Streptomyces/efeitos dos fármacos , Streptomyces/genética , Streptomyces/efeitos da radiação , Raios UltravioletaRESUMO
The illegitimate recombination between S. aureus plasmids pE194 (or pGG20-the hybrid between pE194 and E. coli plasmid pBR322) and pBD17 (plasmid pUB110 without Hpa-II-C-fragment) in B. subtilis was studied. Plasmid cointegrates were generated with the frequency of 1-3.10(-8). Among the 22 hybrids analysed 9 types of recombinants were found. Nucleotide sequences of all the parental plasmids were involved in intermolecular recombination. Nucleotide sequencing of recombinant DNA junctions has revealed that in 8 cases recombination occurred between short homologous regions (9-15 b.p.). One of the recombinants resulted from nonhomologous recombination. The similarity between nucleotide sequences of recombination sites of two types of contegrates and those used for pE194 integration into the B. subtilis chromosome (Bashkirov et al. 1987) was demonstrated. Possible mechanisms of illegitimate recombination are discussed.
Assuntos
Bacillus subtilis/genética , DNA Bacteriano/genética , Plasmídeos , Recombinação Genética , Dados de Sequência Molecular , Homologia de Sequência do Ácido NucleicoRESUMO
The illegitimate recombination between Staphylococcus aureus plasmids pE194 (or pGG20, the hybrid between pE194 and Escherichia coli plasmid pBR322) and pBD17 (plasmid pUB110 without HpaII C-fragment) was studied in Bacillus subtilis. Cointegrates were generated with the frequency of 1-3 X 10(-8). Among 22 hybrids analysed 9 types of recombinants were found. Nucleotide sequences of all three parental plasmids were involved in intermolecular recombination. Nucleotide sequencing of recombinant DNA junctions revealed that in 8 cases recombination occurred between short homologous regions (9-15 bp). One recombinant was formed using nonhomologous sites. The similarity was demonstrated between nucleotide sequences of the recombination sites of two types of cointegrates and those used for pE194 integration into the B. subtilis chromosome. Possible mechanisms of illegitimate recombination are discussed.
Assuntos
Bacillus subtilis/genética , DNA Bacteriano/genética , Plasmídeos , Recombinação Genética , Sequência de Bases , Dados de Sequência Molecular , Homologia de Sequência do Ácido NucleicoRESUMO
A method for obtaining mutations in Bacillus subtilis using integration into the chromosome of the plasmid pHV60 ligated to chromosomal DNA fragments was developed. Auxotrophic mutants acquire, in addition, chloramphenicol-resistance, due to insertion of appropriate plasmid determinants. Chromosomal localization was established and the properties of several mutants were studied.
