In Situ Structures Of The Flagellar Motor And Other Nanomachines Of Helicobacter Pylori

Helicobacter pylori,a helical gram-negative bacterium,colonizes in the stomach and can cause gastrointestinal diseases,such as gastritis.It’s known that the motility mediated by flagella and capacity of releasing virulence factor play important roles in H.pylori pathogenesis.Therefore,an in-depth structural characterization of the nanomachines relative to its motility and virulence releasing can provide important information for the prevention and control of H.pylori.Here,the cryo-Electron Tomography(cryo-ET),combined with sub-tomogram averaging were applied to the wild type andΔfliG、ΔfliY、ΔfliY_N mutants to study the in situ structures of H.pylori and its flagellar motors.The cag-type IV secretion system like(cag-T4SS like)structure in H.pylori was also studied.All the results are listed below:1、The detail in situ structures of H.pylori,including the sheathed flagella,chemoreceptor arrays,flagellar motor are resolved.2、By sub-tomogram averaging,the detail structures of the flagellar motor complex in wild type H.pylori are also presented.The flagellar motor structure not only reveals the locations and structures of several conserved components,including C ring,stator,MS ring,rod,P ring,L ring,but also demonstrates some unique features including the cage with apparent 18-fold symmetry.3、Several flagella assembly intermediates in wild type H.pylori are obtained.A putative model of flagella assembly in H.pylori,by comparision with the intact flagella structure,is proposed here.4、Comparing the flagellar motor structure of several mutants with that of wild type H.pylori,the results show that the C terminal of FliY affects the C ring and soluble export apparatus assembly.Also it gives a clue that FliG plays an indispensable role at the initial stage of the motor assembly of H.pylori.5、In severalΔfliY_N mutants,we observe turbular densities,refered as the cag-T4SS pilus in H.pylori.Also the cag-T4SS like densities are existed in reconstructions of all types of H.pylori,including the wild type and mutants.6、The cag-T4SS like densities are observed in both wild type and mutants.The sub-tomogram average results reveal the in situ three-dimensional cag-T4SS like structure of H.pylori in uninfected state.