Peptidoglycan maturation enzymes affect flagellar functionality in bacteria

Summary The flagellar machinery is a highly complex organelle composed of a free rotating flagellum and a fixed stator that converts energy into movement. The assembly of the flagella and the stator requires inter- actions with the peptidoglycan layer through which the organelle has to pass for externalization. Lytic transglycosylases are peptidoglycan degrading enzymes that cleave the sugar backbone of peptidog- lycan layer. We show that an endogenous lytic trans- glycosylase is required for full motility of Helicobacter pylori and colonization of the gastric mucosa. Defi- ciency of motility resulted from a paralysed phenotype implying an altered ability to generate flagellar rota- tion. Similarly, another Gram-negative pathogen Sal- monella typhimurium and the Gram-positive pathogen Listeria monocytogenes required the activity of lytic transglycosylases, Slt or MltC, and a glucosaminidase (Auto), respectively, for full motility. Furthermore, we show that in absence of the appropriate lytic transgly- cosylase, the flagellar motor protein MotB from H. pylori does not localize properly to the bacterial pole. We present a new model involving the maturation of the surrounding peptidoglycan for the proper anchoring and functionality of the flagellar motor.