title: Genetic analysis of the actinomycin-producing determinants (plasmid) in Streptomyces parvulus using the protoplast fusion technique.
abstract: Doubly auxotrophic, actinomycin-producing and nonproducing strains of Streptomyces parvulus were crossed by protoplast fusion. A strong bias toward the act+ character was noted in all recombinant classes obtained. Analysis of four nutritional markers revealed that they are ordered on a circular linkage map as follows: ura-lys-met-rib-(ura). This sequence resulted in the lowest frequency (2.4-3.4%) of quadruple crossover (QCO) recombinants. Inclusion of the property of actinomycin production in this sequence resulted in a much more greater minimum frequency of QCO recombinants (3-4 times higher). Moreover, the location of the act character minimizing the QCO frequency varied from cross to cross despite the fact that fusion of the act- strains did not yield act+ recombinants. It is concluded that actinomycin synthesis is determined (or controlled) by an episomic factor(s).
mesh_terms: D002874:Chromosome Mapping; D004269:DNA, Bacterial / Q000235:genetics; D003609:Dactinomycin / Q000096:biosynthesis*; D008040:Genetic Linkage; D010957:Plasmids; D011995:Recombination, Genetic; D013302:Streptomyces / Q000235:genetics*
chemical_list: D004269:DNA, Bacterial; D003609:Dactinomycin