Formation of protoplasts ofFusarium culmorum by strepzyme

Spherical protoplast-like structures can be liberated from hyphae ofFusarium culmorum by the action of an enzyme preparation obtained from the cell-free supernatant of the growth medium ofStreptomyces RA. In a previous publication this lytic system was named strepzyme. Treatment was carried out in a citrate phosphate buffer containing 0.8m mannitol or KCl as a stabilizing agent. If the concentration of the stabilizer was lowered to less than 0.2m the protoplasts lysed. These osmotically sensitive structures vary largely in size, are resistant to high speed centrifugation, and stable when kept in the cold. Protoplasts from other molds could also be obtained. The protoplasts could be observed to emerge through pores in the hyphal wall leaving behind delicate but rigid empty cell walls resistant to enzymic digestion and recognizable under the phase-contrast microscope. After sudden and complete lysis of protoplasts some membrane structures were observed. Attempts to obtain electron micrographs of the latter have failed. It was concluded that in the strain ofFusarium studied the strepzyme removes some constituent of the cell wall facilitating the extrusion of the protoplasts.