Natural Genetic Transformation: A Direct Route to Easy Insertion of Chimeric Genes into the Pneumococcal Chromosome.

The ability of Streptococcus pneumoniae (the pneumococcus) to transform is particularly convenient for genome engineering. Several protocols relying on sequential positive and negative selection strategies have been described to create directed markerless modifications, including deletions, insertions, or point mutations. Transformation with DNA fragments carrying long flanking homology sequences is also used to generate mutations without selection but it requires high transformability.

Direct involvement of DprA, the transformation-dedicated RecA loader, in the shut-off of pneumococcal competence.

Natural bacterial transformation is a genetically programmed process allowing genotype alterations that involves the internalization of DNA and its chromosomal integration catalyzed by the universal recombinase RecA, assisted by its transformation-dedicated loader, DNA processing protein A (DprA). In Streptococcus pneumoniae, the ability to internalize DNA, known as competence, is transient, developing suddenly and stopping as quickly. Competence is induced by the comC-encoded peptide, competence stimulating peptide (CSP), via a classic two-component regulatory system ComDE.