Streptococcal competence for genetic transformation: regulation by peptide pheromones

Although the capacity for genetic transformation is perhaps the most famous attribute of pneumococcus, use of this genetic phenomenon as a tool for study of the biology of the organism and of its pathogenicity has been largely restricted to a few favored unencapsulated strains, both by the delicacy of the conditions required for development of competence, and by experience that encapsulated strains transformed poorly. We discuss here the recent discovery of a small stable inexpensive peptide pheromone that acts as a quorum-sensing signal and that induces competence under a wide variety of conditions and in encapsulated strains. Its use circumvents some if not all limitations to the expression of transformability in pneumococcus and therefore expands opportunities for application of tools molecular genetics to many strains of pneumococcus without prior genetic manipulation.