Final Report Summary - MOLSTRUCTTRANSFO (Molecular and Structural Biology of Bacterial Transformation)
During this project, we aimed at acquiring a detailed understating of the molecular mechanism of each of these steps. We studied the composition, architecture and function of the molecular machines involved in these processes. More than core 20 proteins were genetically identified as being required for this process. We isolated these proteins, studied their network of interaction among them and systematically studied their function in vitro and in vivo. For some of them, we managed to obtain crucial insights about their structure and function. In particular, we discovered a new appendage at the surface of S. pneumoniae cells and showed that this appendage is similar in morphology and composition to appendages called Type IV pili commonly found in Gram-negative bacteria. We demonstrated that this new pneumococcal pilus is essential for transformation and that it directly binds DNA. We also identified a new key ATPase called RadA involved in the recombination process. We determined its crystal structure and identified its function in vitro and in vivo. We could show that this protein is a DnaB-type helicase that is recruited by the recombinase RecA at the recombination site to promote strand exchange and therefore promote the recombination process. RadA is crucial for an efficient transformation process but is also involved in genome maintenance is all bacterial species.
Overall, this project laid the foundations of a longer-term project that will eventually solve the central question of the molecular mechanism(s) of bacterial transformation and more broadly of bacterial adaptability processes.