[Use of the protoplast fusion and regeneration method for screening antibiotic producers among inactive strains of Streptomyces].

Intraspecies fusion of protoplasts of two strains of Streptomyces fradiae, i.e native protoplasts of an inactive strain INA 00708 and heat inactivated protoplasts of a neomycin-producing strain ATCC 10745, and regeneration of the protoplasts of the inactive strain INA 00708 resulted in formation of clones producing neomycin and clones synthesizing antibiotics of an unknown nature differing from neomycin. All the active clones were unstable and lost their antibiotic activity in subcultures.

[Protoplast fusion in Streptomyces fradiae strains producing neomycin and tylosin].

Interspecies fusion of protoplasts of the Streptomyces fradiae strains producing neomycin (an aminoglycoside antibiotic) and tylosin (a macrolide antibiotic) was performed with a view to isolate strains producing novel antibiotics. Fusion of the protoplasts of the neomycin- and tylosin-producing strains labelled by the resistance to monomycin and lincomycin, respectively, caused no formation of stable strains producing antibiotics differing in chromatographic mobility from the antibiotics produced by the initial strains. In fusion of the protoplasts of the unlabelled strains, heat-inactivated protoplasts of the active line of one strain (donor) and native protoplasts of the inactive line of the other strain (recipient) were used.

[Comparative study of Streptomyces--producer of aminoglycoside antibiotics, monomycin and kanamycin, and the strain 344 obtained by fusion of their protoplasts by the method of restrictive total DNA fingerprinting].

The method of total DNA restriction finger prints was applied to the study of Streptomyces monomycini INA 1465 producing monomycin, Streptomyces kanamyceticus INA K-13 producing kanamycin and strain 344 isolated after fusion of the protoplasts of strain 1465 and K-13, which produced albofungin and chloralbofungin, aminoglycoside antibiotics. For preparing the finger prints of the strains splitting by endonucleases BamHI, PstI, PvuII, and BgIII was used. The finger prints showed that strain 344 was related to the strain of S.

[Albofungin formation by a strain isolated as a result of fusion of protoplasts of organisms producing aminoglycoside antibiotics].

Strain 344 synthesizing an antibiotic complex was isolated after fusion of the protoplasts of Streptomyces monomycini producing monomycin and Streptomyces kanamyceticus producing kanamycin. The major component of the complex was identified with albofungin and the minor one was suggested to be chloralbofungin. In the cultures of strain 344 variants forming monomycin were detected.

[Effect of protoplast formation and regeneration on the production of nebramycin complex in Streptomyces cremeus subsp. tobramycini].

Production of the nebramycin complex in Streptomyces cremeus subsp. tobramycini before and after the protoplast formation and regeneration was comparatively studied. The antibiotic production was estimated by the total activity and component composition of the nebramycin complex.

[Nucleotide specificity of sibiromycin interaction with DNA].

Sibiromycin binds selectively to poly(dG).poly (dC) and poly(dG--dC).poly (dG--dC) and does not interact with poly(dA--dT).

[Density gradient ultracentrifugation method of studying sibiromycin interaction with linear and circular DNA].

Sibiromycin added to linear chromosomal E. coli DNA in vitro leads to the decrease of bouyant density in neutral CsCl density gradient. This decrease is a linear function of sibiromycin/DNA ratio and amounts to about 32 mg/ml at the ratio equal to 0.

[Role of the functional groups of the sibiromycin molecule in DNA binding].

Biological activity of 2 derivatives of sibiromycin, an antibiotic close by its chemical structure to antramycin and their capacity for formation of complexes with DNA was studied. Anhydrosibiromycin like sibiromycin formed a complex with DNA. The antibiotic increased the DNA melting point but to a less extent than sibiromycin.

[Anthracycline antibiotic, beromycin. The formation of complexes with DNA and the suppresion of nucleic acid biosynthesis].

Beromycin, an antitumor anthracycline antibiotic formed in vitro complexes with native and denaturated DNA and ribosomal RNA. Beromycin had a comparatively low constant of DNA binding and to a less extent increased the melting temperature and viscosity of DNA than the other anthracycline antibiotics. A peculiar property of beromycin was very slow binding with DNA, the complex formation was completed in 60 minutes.