The birth and the development of molecular biology and, subsequently, of genetic engineering and biotechnology cannot be separated from the advancements in our knowledge of the genetics, biochemistry and physiology of bacteria and bacter- phages. Also most of the tools employed nowadays by biotechnologists are of bacterial (or bacteriophage) origin and the playground for most of the DNA manipulations still remains within bacteria. The relative simplicity of the bacterial cell, the short gene- tion times, the well defined and inexpensive culturing conditions which characterize bacteria and the...