The regulation and assembly of the flagellum in Bacillus subtilis.

摘要

Bacteria can build fantastically complex nano-machines to perform a variety of physiological activities. Two examples of these nano-machines are the flagellum and the injectisome. The flagellum is found in many bacterial species including Salmonella enterica and Bacillus subtilis, and functions like a propeller to generate the force necessary to conduct swarming motility. The injectisome is found in pathogenic bacteria including Yersinia pestis and Yersinia enterocolitica, and functions like a molecular needle to inject effector molecules into host cells so that the pathogen can both hide from the host's immune system and make nutrients available for uptake. The understanding of the temporal regulation of assembly and control of the subsequent activity of these nano-machines is critical to our understanding of biological multicomponent machines so that we may identify targets for therapeutics. Here I describe and compare three levels of regulation that affect the assembly and function of the flagellum and the injectisome. I then describe a novel regulator of flagellar assembly, SwrB, where I use exogenic suppressors of swrB to show that SwrB promotes flagellar assembly through the essential export apparatus protein, FliP, as well as the rotor protein, FliG. From my investigations I infer that SwrB functions as an early checkpoint in flagellar assembly. Finally, I identify residues within SwrB that are essential for its ability to promote flagellar assembly. From my analysis, I infer that SwrB localizes at the cell membrane via its N-terminal transmembrane domain where it may interact with additional proteins to promote flagellar assembly through its C-terminal functional domain.