Défense de thèse de doctorat en sciences biologiques

Deciphering the PTSNtr regulatory functions in Caulobacter crescentus : a pathway controlling cell cycle according to nutrient availability

Jury

Boris GOERKE (University of Vienna), Justine COLLIER CLOSE (University of Lausanne), Xavier DE BOLLE (UNamur), Jean-Jacques LETESSON, président (UNamur), Régis HALLEZ, promoteur (UNamur)

Résumé

A plethora of new regulatory functions associated with the nitrogen-related phosphoenolpyruvate phosphotransferase system (PTS^Ntr) have been discovered in bacteria these recent years. During my thesis, I characterized at the molecular level the involvement of PTS^Ntr in the control of Caulobacter crescentus asymmetric cell cycle. Upon nitrogen starvation, we found the overphosphorylated PTS^Ntr proteins HPr_His~P and EIIA^Ntr~P regulate cell cycle progression by (i) modulating SpoT synthetase and hydrolase activity, and thereby (p)ppGpp levels, as well as by controlling phosphate homeostasis, by interfering with PhoB activity. Our results suggest that HPr_His~P directly inhibits PhoR kinase activity independently of (p)ppGpp. This work illustrates that the PTS^Ntr coordinates cell cycle and cellular metabolic state by modulating the (p)ppGpp and the Pho regulon. This work might lay the foundation for further studies on the intertwining of phosphate, nitrogen and potentially carbon metabolisms and their consequences on Caulobacter cell cycle.

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