Acta Biologica 29. (1978)
2. szám - Fehér Zs.–Szabó G.: Genetic relatedness between streptomycin-producing and non-producin strains of Streptomyces griseus, studied by means of DNA-DNA hybridization
Acta biol. Acad. Sei. hung. 29 (2), 165 —171 (1978) GENETIC RELATEDNESS BETWEEN STREPTOMYCIN-PRODUCING AND NON-PRODUCING STRAINS OF STREPTOMYCES GRISEUS, STUDIED BY MEANS OF DNA-DNA HYBRIDIZATION Zs. Fehér and G. Szabó DEPARTMENT OF BIOLOGY, UNIVERSITY MEDICAL SCHOOL, DEBRECEN, HUNGARY (Received 1978 — 04 — 10) Abstract DNA-DNA hybridization was studied in order to determine the genetic relatedness between a streptomycin-producing and a non-producing mutant of Streptomyces griseus. The latter strain of short vegetative life cycle had been developed from the streptomycin-producing strain by means of nitrogen mustard treatment. Since the two strains differ in several features, we were prompted to examine the sequence homology between their DNAs. Hybridization experiments carried out with the membrane filter method yielded 73.8% and 67.3% DNA homology values, respectively. The results indicate that there is a significant, but not very close, relatedness between the DNA sequences that corresponds to the similarities and differences observed between the phenotypes of the two strains. Further aspects of established homology are also discussed. Introduction In order to understand their biological significance and the function antibiotics have in the life of the producing strain, two mutants of Streptomyces griseus have been investigated in our Institute. S. griseus No. 52-1, a streptomycin-producing (SM-producing) mutant, which is closely related to industrial strains, does not sporulate in submerged culture, i. e. its development is blocked. S. griseus No. 45-H, a streptomycin-non-producing (SM-non-producing) mutant, has complete life cycle; it sporulates well in submerged fermentation [20]. The latter strain has been obtained from the SM-producing one by nitrogen mustard treatment [16]. Comparison of the two strains reveals that they differ significantly in their life cycle [22], the pentose-hexose ratio in the cell wall [1, 3], the quantity of the cell wall in the vegetative mycelia [3], the amino acid composition of their mucopeptide [4], the heat resistance of their spores [7, 23] and their capability to germinate on and utilize different carbon sources [16]. At the same time the fact that streptidine, a component of the SM molecule, can be isolated from the cell wall of the SM-non-producing strain indicates certain relatedness between the two strains [2, 3]. 5 Acta Biologica Academiae Scientiarurn Hungaricae 29, 1978