Possible plasmid involvement in turimycin production in Streptomyces hygroscopicus.

Streptomyces hygroscopicus JA 6599 is the producer of the macrolide antibiotic turimycin. Mapping analysis by conventional matings and protoplast fusion techniques were carried out. The sequence of auxotrophic markers determined by using the method of minimizing the frequency of quadruple crossover recombinants, could be shown to be in accordance with the related marker sequence of Streptomyces coelicolor after both conjugation and protoplast fusion. However, the tur locus could localized between chromosomal markers only assuming quadruple crossover. Moreover, after conventional crosses the tur marker has to be localized at quite another site than after protoplast fusion. Regarding also our results on the evidence of extrachromosomal DNA in strains of S. hygroscopicus, the following hypothesis is proposed: the structural genes for turimycin biosynthesis are localized on the bacterial genome, but plasmid-borne genes might be involved in the control of the antibiotic production in a yet unknown way, possibly by inducing chromosomal rearrangements.