Bacteria evolved mechanisms to adapt to their fluctuating environments, by sensing any variations and to appropriately react to them. The production of an alarmone, the hyperphosphorylated guanosine called (p)ppGpp constitutes one of these mechanisms. This signalling molecule accumulates when nutrients become limiting. Once produced, (p)ppGpp will deeply modify the transcriptional and translational landscapes of bacterial cells in order to concentrate their resources to face starvation. Although the involvement of (p)ppGpp in bacterial stress response is well known for decades, mechanisms sensing specific nutrient stravation and accordingly regulating (p)ppGpp levels remains mostly unknown. Recently, our lab described the nitrogen-related phosphoenolpyruvate phosphotransferase system (PTSNt) as one of these mechanism allowing (p)ppGpp accumulation during a nitrogen stress in Caulobacter crescentus. Three PTSNt components (EIN, Hpr and EIIANt) have been shown to be involved in the regulation of the (p)ppGpp synthetase/hydrolase SpoT. In particular, it was found that the last protein of the phosphorelay — EILANt - interacts with SpoT to specifically inhibit its hydrolase activity. However, a fourth component called EIA and encoded by the ptsM gene was never studied so far. In this work, we characterized the regulations of the EIIANprotein as well as the potential role played by EIIA in the nutrient stress response of C. crescentus. Finally, we also searched for potential new regulators SpoT by using a Tn-seq approach. Our study allowed to identify EIIA as a regulator of HPr as well as to list potential new activators and inhibitors of SpoT that should be further characterized in the future.
|la date de réponse||2017|
|Superviseur||Regis Hallez (Promoteur)|