Interspecific Electrofusion between Protoplasts of Streptomyces antibioticus and Streptomyces fradiae

Abstract

The interspecific electrofusion between protoplasts of Streptomyces antibioticus a20 (Ala⁻) and S. fradiae f2 (His⁻) was examined. The pulse intensities required for the breakdown of half of the protoplasts were 7kV/cm for S. antibioticus a20 and 5kV/cm for S. fradiae f2. The optimum pulse intensity for the fusion was found to be 6 kV/cm. When the density of a protoplast suspension was 1 × 10⁸ protoplasts/ml in a 0.3 m sucrose solution containing 2.5 mm MgCl₂ and CaCl₂, the maximum fusion frequency of 2.7% was obtained on the application of one square field pulse of 6kV/cm for 20_iusec after dielectrophoresis in an alternating field of 800V/cm (1 MHz) for 60 sec. The fusion frequency was much higher than that obtained on polyethyleneglycol-induced fusion (0.15%). This is the first case of electrofusion of Streptomyces protoplasts, which are as small as those of some bacteria.