Title: Improvements of protoplast transformation in Staphylococcus carnosus
Abstract: Protoplast transformation is so far the only method to transfer plasmids into Staphylococcus carnosus. However, the preparation of new protoplasts for each transformation is time-consuming and the quality of the protoplasts may also vary each time. An improved method is described which allows the storage of the protoplasts deep frozen (at − 70°C) for several months without affecting their transforming capability. The possibility of keeping protoplasts competent for a long period opens several advantages: the transformation can be carried out immediately, the transformation procedure is reduced to only a couple of minutes, and the protoplasts of one batch have the same quality, yielding a more constant transformation frequency.