Strategies for the development of bacterial transformation systems.

An effective transformation system is a prerequisite for facile genetic manipulation of bacteria. Bacteria may be naturally competent for transformation or may be treated with various agents, such as Tris buffers or divalent metal ions, to induce competence. Transformation can also be accomplished by electroporation, or by fusion of protoplasts with PEG in the presence of transforming DNA. Unfortunately, the mechanism by which cells become permeable to DNA and the process by which DNA enters the cells is frequently unknown. In order to establish a transformation system for an untransformable bacterium, recipient strains and transforming DNA must be carefully selected. Since it is impossible to predict in advance which method of transformation will be successful with a particular bacterial strain, several techniques are usually evaluated. This review describes a number of factors that appear to be critical for developing a transformation system and presents a strategy for experimentation with novel bacteria.