Abstract
Protoplast formation and regeneration procedures were developed for lactic acid bacteria. Initial attempts to fuse the protoplasts using an electric field were unsuccessful. No fusion was observed and the protoplasts lysed when the electric field voltage was increased to 24kV/cm. However, fusion products were obtained when the protoplasts were suspended in subfusion concentrations (<20%) of polyethylene glycol (PEG) and exposed to D. C. current. Also, the PEG protected protoplasts against lysis in current fields up to 72kV/cm. The frequency of hybrid cell formation (i.e. plasmid transfer) via the electric field-induced fusion was equivalent to the plasmid transfer frequency obtained via conjugation. Chemically induced fusion resulted in a transfer frequency of an order of magnitude greater than that of conjugation.
