Fusion of Bacillus subtilis and Bacillus licheniformis protoplasts. The mapping of the mutations leading to the supersynthesis of riboflavin in interspecies hybrids

: As a result of fusion of the protoplasts of B. subtilis and B. licheniformis the majority of the prototrophic hybrids, as well as the auxotrophs with the Thi-Hom-phenotype or the Thi-phenotype acquired capacity for over-production of riboflavin lacking in the initial parent strains. When grown on the minimal Spizizen medium with aeration at 37 degrees C the auxotrophic recombinants accumulated 10-60 micrograms/ml of riboflavin for 2 days, while the prototrophic recombinants accumulated up to 90 micrograms/ml of riboflavin. The respective figures for their cultivation in the sucrose fermentation medium were 100-330 and 600 micrograms/ml. For mapping 3 random variants of them with different phenotypes, i.e. SL-7 (prototroph), SL-15 Thi-and SL-52 Thi-Hom-were used. Localization of the mutation on the chromosome of B. subtilis was based on transformation experiments with three marker crossing, where hybrid strains SL-7, S1-15 and SL-52 were used as the DNA donor and strain lys-rib-of B. subtilis was used as the recipient. The analysis showed that the required mutation designated as R1 was localized on the chromosome of B. subtilis in the regulatory region rib0 of the riboflavin operon.