This paper is an outline of initial idea and experimental process of our research which has been carried out in our laboratory of National Institute of Health, Japan, for 25 years from 1964 to 1988. The research is divided into 4 fields.
1. On the basis of DNA homology, the determination of systematic relation among 30 species of
Streptomyces and the evaluation of taxonomic criteria for species identification. In this study, method for the determination of DNA homology, DNA homology of 30 species in a so-called Griseus group, their systematic relation, and evaluation of species-identifying character were described.
2. Basic technology for introduction of actinophage DNA into streptomycete protoplasts and regeneration of the protoplasts to mycelial form.
3. Involvement of plasmid genes in antibiotic production. The contents of this research were concerned in the suggestive phenomena of plasmid involvement in antibiotic production, the physical detection of the flower-shape DNA suggesting a type of plasmids, the genetical evidence of plasmid involvement in chloramphenicol production, the genetic mapping of chloramphenicol biosynthetic genes and the role of plasmid genes in its production, the isolation of ccDNA from 8 species of
Streptomyces including
S. kasugaensis, and the function of plasmid genes in aureothricin and kasugamycin production.
4. Development of host-vector systems in
Streptomyces. Pathogenicity, survival activity of DNase and restriction enzyme activity of
S. kasugaensis as a host, the preparation of mec- mutant as a more safety host, the nucleotide sequence of the mec+ gene, the cloning of extracellular xylanase gene and determination of its nucleotide sequence, the construction of secretion vectors using its xylanase gene, and the mutual relation of three pock-forming plasmids resident in
S. noursei were described and discussed.
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