Protoplast isolation and regeneration in Streptomyces clavuligerus.

The regeneration of streptomycete protoplasts is a major step following genetic manipulations such as fusion and DNA-mediated transformation. Reports of studies on the regeneration of protoplasts from Streptomyces clavuligerus are limited and for this reason the experiments described in this paper were carried out. An investigation of protoplast formation and cytology was made to gain further insight into the loss of protoplast viability in osmotically stabilized support media. Protoplasts with the highest regeneration frequency were isolated from mycelium, grown in a two-stage culture system (without glycine), using lysozyme dissolved in a sucrose osmoticum containing 1% bovine serum albumin. The latter promoted improved protoplast viability. A systematic survey was made of the components of regeneration medium R5, previously used for S. clavuligerus, and other potentially advantageous components and conditions, in an attempt to raise the regeneration frequency of the protoplasts. An improved regeneration medium (R6) and protocol which supported higher and more consistent levels of regeneration of S. clavuligerus protoplasts resulted from these experiments. These improved procedures for protoplast isolation and regeneration proved to be suitable for other streptomycete species.