9506785 Morrison Pneumococcal transformation is a naturally occurring, inducible gene replacement mechanism that is relatively simple and very efficient. Competence for genetic transformation in pneumococcus (Streptococcus pneumoniae) occurs during a brief period of highly specialized protein synthesis, coordinated among all cells of an actively growing culture by a secreted 17-residue peptide pheromone. During a period of approximately 10-20 minutes, the competent cells can transport DNA into the cytoplasm and replace homologous genes I the chromosome very efficiently. In identifying and cloning genes involved in this DNA-processing mechanisms, and in determining their roles, this study relies on standard genetic techniques and the efficient gene replacement provided by the natural transformation process itself, in combination with molecular methods in vitro, a rapid physical mapping method, and recombinant DNA cloning using new vectors in pneumococcus and in E. coli. Induced genes are identified by insertion of a lacZ reporter gene. These studies identify, map, clone, and sequence genes of this natural transformation system in two broad areas: (a) genes of the pathway that transports DNA into the cell and processes it for genetic recombination, and (b) genes regulating the induction of this pathway via a quorumsensing peptide signal. %%% This research provides an understanding of how bacteria naturally exchange genes. It is therefore, useful in understanding how genes for new properties can appear in a bacterial population. ***
