Fine‐tuning cellular levels of DprA ensures transformant fitness in the human pathogen Streptococcus pneumoniae Streptococcus pneumoniae

摘要

Summary Natural genetic transformation is a widespread mechanism of horizontal gene transfer. It involves the internalization of exogenous DNA as single strands and chromosomal integration via homologous recombination, promoting acquisition of new genetic traits. Transformation occurs during a distinct physiological state called competence. InStreptococcus pneumoniae , competence is controlled by ComDE, a twocomponent system induced by an exported peptide pheromone. DprA is universal among transformable species, strongly induced during pneumococcal competence, and crucial for pneumococcal transformation. Pneumococcal DprA plays three crucial roles in transformation and competence. Firstly, DprA protects internalized DNA from degradation. Secondly, DprA loads the homologous recombinase RecA onto transforming DNA to promote transformation. Finally, DprA interacts with the response regulator ComE to shutoff competence. Here, we explored the effect of altering the cellular levels of DprA on these three roles. High cellular levels of DprA were not required for the primary role of DprA as a transformationdedicated recombinase loader or for protection of transforming DNA. In contrast, full expression ofdprA was required for optimal competence shutoff and transformant fitness. High cellular levels of DprA thus ensure the fitness of pneumococcal transformants by mediating competence shutoff. This promotes survival and propagation of transformants, maximizing pneumococcal adaptive potential.