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Abstract
Conditions for the regeneration of cells from protoplasts of Streptomyces chrysomallus, a producer of the peptide antibiotic actinomycin, are described. Regeneration of fusion products was most efficient at 27–30 °C on regeneration R2 medium ( Okanishi et al., 1974 ) containing 0·25 m-sucrose. The addition of phosphate (150–300 mg 1−1) to the medium and incubation at 23 °C proved to be optimal for the regeneration of individual strains. Highest recombination frequencies after protoplast fusion were obtained by fusing protoplasts in the presence of 45% (w/v) polyethylene glycol 6000. With strains that produce no, or little antibiotic, protoplasts must be present in excess in fusion mixtures in order to overcome inhibition of regeneration by the antibiotic-producing partner.
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