scholarly journals Imaging the Motility and Chemotaxis Machineries in Helicobacter pylori by Cryo-Electron Tomography

2016 ◽  
Vol 199 (3) ◽  
Author(s):  
Zhuan Qin ◽  
Wei-ting Lin ◽  
Shiwei Zhu ◽  
Aime T. Franco ◽  
Jun Liu
Keyword(s):  
Helicobacter Pylori ◽  
Molecular Mechanisms ◽  
Electron Tomography ◽  
Bacterial Pathogen ◽  
Human Stomach ◽  
Content Type ◽  
Flagellar Motors ◽  
Cryo Electron Tomography ◽  
Flagellar Assembly ◽  
H Pylori

ABSTRACT Helicobacter pylori is a bacterial pathogen that can cause many gastrointestinal diseases, including ulcers and gastric cancer. A unique chemotaxis-mediated motility is critical for H. pylori to colonize in the human stomach and to establish chronic infection, but the underlying molecular mechanisms are not well understood. Here, we employ cryo-electron tomography (cryo-ET) to reveal detailed structures of the H. pylori cell envelope, including the sheathed flagella and chemotaxis arrays. Notably, H. pylori possesses a distinctive periplasmic cage-like structure with 18-fold symmetry. We propose that this structure forms a robust platform for recruiting 18 torque generators, which likely provide the higher torque needed for swimming in high-viscosity environments. We also reveal a series of key flagellar assembly intermediates, providing structural evidence that flagellar assembly is tightly coupled with the biogenesis of the membrane sheath. Finally, we determine the structure of putative chemotaxis arrays at the flagellar pole, which have implications for how the direction of flagellar rotation is regulated. Together, our pilot cryo-ET studies provide novel structural insights into the unipolar flagella of H. pylori and lay a foundation for a better understanding of the unique motility of this organism. IMPORTANCE Helicobacter pylori is a highly motile bacterial pathogen that colonizes approximately 50% of the world's population. H. pylori can move readily within the viscous mucosal layer of the stomach. It has become increasingly clear that its unique flagella-driven motility is essential for successful gastric colonization and pathogenesis. Here, we use advanced imaging techniques to visualize novel in situ structures with unprecedented detail in intact H. pylori cells. Remarkably, H. pylori possesses multiple unipolar flagella, which are driven by one of the largest flagellar motors found in bacteria. These large motors presumably provide the higher torque needed by the bacterial pathogens to navigate in the viscous environment of the human stomach.

scholarly journals In SituStructures of Polar and Lateral Flagella Revealed by Cryo-Electron Tomography

2019 ◽  
Vol 201 (13) ◽  
Author(s):  
Shiwei Zhu ◽  
Maren Schniederberend ◽  
Daniel Zhitnitsky ◽  
Ruchi Jain ◽  
Jorge E. Galán ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Electron Tomography ◽  
Additional Insight ◽  
Content Type ◽  
Bacterial Flagellum ◽  
Cryo Electron Tomography ◽  
Serovar Typhimurium ◽  
Flagellar Assembly ◽  
Insight Into

ABSTRACTThe bacterial flagellum is a sophisticated self-assembling nanomachine responsible for motility in many bacterial pathogens, includingPseudomonas aeruginosa,Vibriospp., andSalmonella enterica. The bacterial flagellum has been studied extensively in the model systemsEscherichia coliandSalmonella entericaserovar Typhimurium, yet the range of variation in flagellar structure and assembly remains incompletely understood. Here, we used cryo-electron tomography and subtomogram averaging to determinein situstructures of polar flagella inP. aeruginosaand peritrichous flagella inS. Typhimurium, revealing notable differences between these two flagellar systems. Furthermore, we observed flagellar outer membrane complexes as well as many incomplete flagellar subassemblies, which provide additional insight into mechanisms underlying flagellar assembly and loss in bothP. aeruginosaandS. Typhimurium.IMPORTANCEThe bacterial flagellum has evolved as one of the most sophisticated self-assembled molecular machines, which confers locomotion and is often associated with virulence of bacterial pathogens. Variation in species-specific features of the flagellum, as well as in flagellar number and placement, results in structurally distinct flagella that appear to be adapted to the specific environments that bacteria encounter. Here, we used cutting-edge imaging techniques to determine high-resolutionin situstructures of polar flagella inPseudomonas aeruginosaand peritrichous flagella inSalmonella entericaserovar Typhimurium, demonstrating substantial variation between flagella in these organisms. Importantly, we observed novel flagellar subassemblies and provided additional insight into the structural basis of flagellar assembly and loss in bothP. aeruginosaandS. Typhimurium.

scholarly journals Helicobacter pylori Infections in the Bronx, New York: Surveying Antibiotic Susceptibility and Strain Lineage by Whole-Genome Sequencing

2019 ◽  
Vol 58 (3) ◽  
Author(s):  
Rajagopalan Saranathan ◽  
Michael H. Levi ◽  
Alice R. Wattam ◽  
Adel Malek ◽  
Emmanuel Asare ◽  
...  
Keyword(s):  
Helicobacter Pylori ◽  
Whole Genome Sequencing ◽  
Genome Sequencing ◽  
Molecular Mechanisms ◽  
Kappa Coefficient ◽  
23S Rrna ◽  
Whole Genome ◽  
Content Type ◽  
Phenotypic Resistance ◽  
H Pylori

ABSTRACT The emergence of drug resistance in Helicobacter pylori has resulted in a greater need for susceptibility-guided treatment. While the alleles associated with resistance to clarithromycin and levofloxacin have been defined, there are limited data regarding the molecular mechanisms underlying resistance to other antimicrobials. Using H. pylori isolates from 42 clinical specimens, we compared phenotypic and whole-genome sequencing (WGS)-based detection of resistance. Phenotypic resistance correlated with the presence of alleles of 23S rRNA (A2142G/A2143G) for clarithromycin (kappa coefficient, 0.84; 95% confidence interval [CI], 0.67 to 1.0) and gyrA (N87I/N87K/D91Y/D91N/D91G/D99N) for levofloxacin (kappa coefficient, 0.90; 95% CI, 0.77 to 1.0). Phenotypic resistance to amoxicillin in three isolates correlated with mutations in pbp1, pbp2, and/or pbp3 within coding regions near known amoxicillin binding motifs. All isolates were phenotypically susceptible to tetracycline, although four bore a mutation in 16S rRNA (A926G). For metronidazole, nonsense mutations and R16H substitutions in rdxA correlated with phenotypic resistance (kappa coefficient, 0.76; 95% CI, 0.56 to 0.96). Previously identified mutations in the rpoB rifampin resistance-determining region (RRDR) were not present, but 14 novel mutations outside the RRDR were found in rifampin-resistant isolates. WGS also allowed for strain lineage determination, which may be important for future studies in associating precise MICs with specific resistance alleles. In summary, WGS allows for broad analyses of H. pylori isolates, and our findings support the use of WGS for the detection of clarithromycin and levofloxacin resistance. Additional studies are warranted to better define mutations conferring resistance to amoxicillin, tetracycline, and rifampin, but combinatorial analyses for rdxA gene truncations and R16H mutations have utility for determining metronidazole resistance.

scholarly journals The Helicobacter pylori CZB Cytoplasmic Chemoreceptor TlpD Forms an Autonomous Polar Chemotaxis Signaling Complex That Mediates a Tactic Response to Oxidative Stress

2016 ◽  
Vol 198 (11) ◽  
pp. 1563-1575 ◽  
Author(s):  
Kieran D. Collins ◽  
Tessa M. Andermann ◽  
Jenny Draper ◽  
Lisa Sanders ◽  
Susan M. Williams ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Reactive Oxygen Species ◽  
Helicobacter Pylori ◽  
Molecular Mechanisms ◽  
Reactive Oxygen ◽  
Host Cells ◽  
Oxygen Species ◽  
Content Type ◽  
Signaling Complex ◽  
H Pylori

ABSTRACTCytoplasmic chemoreceptors are widespread among prokaryotes but are far less understood than transmembrane chemoreceptors, despite being implicated in many processes. One such cytoplasmic chemoreceptor isHelicobacter pyloriTlpD, which is required for stomach colonization and drives a chemotaxis response to cellular energy levels. Neither the signals sensed by TlpD nor its molecular mechanisms of action are known. We report here that TlpD functions independently of the other chemoreceptors. When TlpD is the sole chemoreceptor, it is able to localize to the pole and recruits CheW, CheA, and at least two CheV proteins to this location. It loses the normal membrane association that appears to be driven by interactions with other chemoreceptors and with CheW, CheV1, and CheA. These results suggest that TlpD can form an autonomous signaling unit. We further determined that TlpD mediates a repellent chemotaxis response to conditions that promote oxidative stress, including being in the presence of iron, hydrogen peroxide, paraquat, and metronidazole. Last, we found that all testedH. pyloristrains express TlpD, whereas other chemoreceptors were present to various degrees. Our data suggest a model in which TlpD coordinates a signaling complex that responds to oxidative stress and may allowH. pylorito avoid areas of the stomach with high concentrations of reactive oxygen species.IMPORTANCEHelicobacter pylorisenses its environment with proteins called chemoreceptors. Chemoreceptors integrate this sensory information to affect flagellum-based motility in a process called chemotaxis. Chemotaxis is employed during infection and presumably aidsH. pyloriin encountering and colonizing preferred niches. A cytoplasmic chemoreceptor named TlpD is particularly important in this process, and we report here that this chemoreceptor is able to operate independently of other chemoreceptors to organize a chemotaxis signaling complex and mediate a repellent response to oxidative stress conditions.H. pyloriencounters and must cope with oxidative stress during infection due to oxygen and reactive oxygen species produced by host cells. TlpD's repellent response may allow the bacteria to escape niches experiencing inflammation and elevated reactive oxygen species (ROS) production.

scholarly journals Lactobacilli Reduce Helicobacter pylori Attachment to Host Gastric Epithelial Cells by Inhibiting Adhesion Gene Expression

2016 ◽  
Vol 84 (5) ◽  
pp. 1526-1535 ◽  
Author(s):  
Nele de Klerk ◽  
Lisa Maudsdotter ◽  
Hanna Gebreegziabher ◽  
Sunil D. Saroj ◽  
Beatrice Eriksson ◽  
...  
Keyword(s):  
Helicobacter Pylori ◽  
Epithelial Cells ◽  
Molecular Mechanisms ◽  
Binding Capacity ◽  
Host Cells ◽  
Gastric Epithelial Cells ◽  
Content Type ◽  
Effector Molecule ◽  
H Pylori

The human gastrointestinal tract, including the harsh environment of the stomach, harbors a large variety of bacteria, of whichLactobacillusspecies are prominent members. The molecular mechanisms by which species of lactobacilli interfere with pathogen colonization are not fully characterized. In this study, we aimed to study the effect of lactobacillus strains upon the initial attachment ofHelicobacter pylorito host cells. Here we report a novel mechanism by which lactobacilli inhibit adherence of the gastric pathogenH. pylori. In a screen withLactobacillusisolates, we found that only a few could reduce adherence ofH. pylorito gastric epithelial cells. Decreased attachment was not due to competition for space or to lactobacillus-mediated killing of the pathogen. Instead, we show that lactobacilli act onH. pyloridirectly by an effector molecule that is released into the medium. This effector molecule acts onH. pyloriby inhibiting expression of the adhesin-encoding genesabA. Finally, we verified that inhibitory lactobacilli reducedH. pyloricolonization in anin vivomodel. In conclusion, certainLactobacillusstrains affect pathogen adherence by inhibitingsabAexpression and thereby reducingH. pyloribinding capacity.

scholarly journals Helicobacter pylori VacA Induces Programmed Necrosis in Gastric Epithelial Cells

2011 ◽  
Vol 79 (7) ◽  
pp. 2535-2543 ◽  
Author(s):  
Jana N. Radin ◽  
Christian González-Rivera ◽  
Susan E. Ivie ◽  
Mark S. McClain ◽  
Timothy L. Cover
Keyword(s):  
Gastric Cancer ◽  
Cell Death ◽  
Helicobacter Pylori ◽  
Epithelial Cells ◽  
Human Stomach ◽  
Gastric Epithelial Cells ◽  
Wild Type ◽  
Programmed Necrosis ◽  
Content Type ◽  
H Pylori

ABSTRACTHelicobacter pyloriis a Gram-negative bacterium that colonizes the human stomach and contributes to the development of peptic ulcer disease and gastric cancer. The secreted pore-forming toxin VacA is one of the major virulence factors ofH. pylori. In the current study, we show that AZ-521 human gastric epithelial cells are highly susceptible to VacA-induced cell death. Wild-type VacA causes death of these cells, whereas mutant VacA proteins defective in membrane channel formation do not. Incubation of AZ-521 cells with wild-type VacA results in cell swelling, poly(ADP-ribose) polymerase (PARP) activation, decreased intracellular ATP concentration, and lactate dehydrogenase (LDH) release. VacA-induced death of these cells is a caspase-independent process that results in cellular release of histone-binding protein high mobility group box 1 (HMGB1), a proinflammatory protein. These features are consistent with the occurrence of cell death through a programmed necrosis pathway and suggest that VacA can be included among the growing number of bacterial pore-forming toxins that induce cell death through programmed necrosis. We propose that VacA augmentsH. pylori-induced mucosal inflammation in the human stomach by causing programmed necrosis of gastric epithelial cells and subsequent release of proinflammatory proteins and may thereby contribute to the pathogenesis of gastric cancer and peptic ulceration.

scholarly journals Complex Cellular Responses of Helicobacter pylori-Colonized Gastric Adenocarcinoma Cells

2011 ◽  
Vol 79 (6) ◽  
pp. 2362-2371 ◽  
Author(s):  
Sabine Schneider ◽  
Gert Carra ◽  
Ugur Sahin ◽  
Benjamin Hoy ◽  
Gabriele Rieder ◽  
...  
Keyword(s):  
Helicobacter Pylori ◽  
Epithelial Cells ◽  
Host Cell ◽  
Cell Lines ◽  
Molecular Mechanisms ◽  
Cellular Responses ◽  
Host Cells ◽  
Human Gastric Mucosa ◽  
Content Type ◽  
H Pylori

ABSTRACTHelicobacter pyloriis an important class I carcinogen that persistently infects the human gastric mucosa to induce gastritis, gastric ulceration, and gastric cancer.H. pyloripathogenesis strongly depends on pathogenic factors, such as VacA (vacuolating cytotoxin A) or a specialized type IV secretion system (T4SS), which injects the oncoprotein CagA (cytotoxin-associated gene A product) into the host cell. Since access to primary gastric epithelial cells is limited, many studies on the complex cellular and molecular mechanisms ofH. pyloriwere performed in immortalized epithelial cells originating from individual human adenocarcinomas. The aim of our study was a comparative analysis of 14 different human gastric epithelial cell lines after colonization withH. pylori. We found remarkable differences in host cell morphology, extent of CagA tyrosine phosphorylation, adhesion to host cells, vacuolization, and interleukin-8 (IL-8) secretion. These data might help in the selection of suitable cell lines to study host cell responses toH. pyloriin vitro, and they imply that different host cell factors are involved in the determination ofH. pyloripathogenesis. A better understanding ofH. pylori-directed cellular responses can provide novel and more balanced insights into the molecular mechanisms ofH. pylori-dependent pathogenesisin vivoand may lead to new therapeutic approaches.

scholarly journals Diversification of the AlpB Outer Membrane Protein of Helicobacter pylori Affects Biofilm Formation and Cellular Adhesion

2016 ◽  
Vol 199 (6) ◽  
Author(s):  
Hideo Yonezawa ◽  
Takako Osaki ◽  
Toshiyuki Fukutomi ◽  
Tomoko Hanawa ◽  
Satoshi Kurata ◽  
...  
Keyword(s):  
Helicobacter Pylori ◽  
Outer Membrane ◽  
Mutant Strain ◽  
Biofilm Formation ◽  
Molecular Mechanisms ◽  
Bacterial Biofilm ◽  
Content Type ◽  
Successful Infection ◽  
H Pylori

ABSTRACT Helicobacter pylori is one of the most common causes of bacterial infection in humans, and it forms biofilms on human gastric mucosal epithelium as well as on in vitro abiotic surfaces. Bacterial biofilm is critical not only for environmental survival but also for successful infection. We previously demonstrated that strain TK1402, which was isolated from a Japanese patient with duodenal and gastric ulcers, has high biofilm-forming ability in vitro relative to other strains. In addition, we showed that outer membrane vesicles (OMV) play an important role in biofilm formation. The aim of this study was to analyze which protein(s) in the OMV contributes to biofilm formation in TK1402. We obtained a spontaneous mutant strain derived from TK1402 lacking biofilm-forming ability. The protein profiles of the OMV were compared between this mutant strain and the wild type, and it was found that AlpB, an outer membrane protein in the OMV of the mutant strain, was markedly decreased compared to that of the wild type. Restoration of TK1402 alpB to the mutant strain fully recovered the ability to form biofilm. However, restoration with alpB from other strains demonstrated incomplete recovery of biofilm-forming ability. We therefore inferred that the variable region of AlpB (amino acid positions 121 to 146) was involved in TK1402 biofilm formation. In addition, diversification of the AlpB sequence was shown to affect the ability to adhere to AGS cells. These results demonstrate a new insight into the molecular mechanisms of host colonization by H. pylori. IMPORTANCE Bacterial biofilm is critical not only for environmental survival but also for successful infection. The mechanism of Helicobacter pylori adherence to host cells mediated by cell surface adhesins has been the focus of many studies, but little is known regarding factors involved in H. pylori biofilm formation. Our study demonstrated that AlpB plays an important role in biofilm formation and that this property depends upon the specific sequence of alpB. This in turn was shown to be important in the ability to adhere to gastric cells. We anticipate that these results will provide new insight into the molecular mechanisms of H. pylori colonization.

scholarly journals The correlation between lncRNAs and Helicobacter pylori in gastric cancer

2019 ◽  
Vol 77 (9) ◽  
Author(s):  
Narges Dastmalchi ◽  
Seyed Mahdi Banan Khojasteh ◽  
Mirsaed Miri Nargesi ◽  
Reza Safaralizadeh
Keyword(s):  
Gastric Cancer ◽  
Helicobacter Pylori ◽  
Molecular Mechanisms ◽  
Gastrointestinal Diseases ◽  
Mechanisms Of Action ◽  
Molecular Pathways ◽  
Gastric Diseases ◽  
Non Coding Rnas ◽  
H Pylori ◽  
The Relationship

ABSTRACT Helicobacter pylori infection performs a key role in gastric tumorigenesis. Long non-coding RNAs (lncRNAs) have demonstrated a great potential to be regarded as effective malignancy biomarkers for various gastrointestinal diseases including gastric cancer (GC). The present review highlights the relationship between lncRNAs and H. pylori in GC. Several studies have examined not only the involvement of lncRNAs in H. pylori-associated GC progression but also their molecular mechanisms of action. Among the pertinent studies, some have addressed the effects of H. pylori infection on modulatory networks of lncRNAs, while others have evaluated the effects of changes in the expression level of lncRNAs in H. pylori-associated gastric diseases, especially GC. The relationship between lncRNAs and H. pylori was found to be modulated by various molecular pathways.

scholarly journals A cryo–electron tomography workflow reveals protrusion-mediated shedding on injured plasma membrane

2021 ◽  
Vol 7 (13) ◽  
pp. eabc6345
Author(s):  
Shrawan Kumar Mageswaran ◽  
Wei Yuan Yang ◽  
Yogaditya Chakrabarty ◽  
Catherine M. Oikonomou ◽  
Grant J. Jensen
Keyword(s):  
Plasma Membrane ◽  
Molecular Mechanisms ◽  
Electron Tomography ◽  
Membrane Damage ◽  
Light And Electron Microscopy ◽  
Actin Dynamics ◽  
Endosomal Sorting ◽  
Plasma Membrane Damage ◽  
Cryo Electron Tomography ◽  
Vacuolar Protein

Cryo–electron tomography (cryo-ET) provides structural context to molecular mechanisms underlying biological processes. Although straightforward to implement for studying stable macromolecular complexes, using it to locate short-lived structures and events can be impractical. A combination of live-cell microscopy, correlative light and electron microscopy, and cryo-ET will alleviate this issue. We developed a workflow combining the three to study the ubiquitous and dynamic process of shedding in response to plasma membrane damage in HeLa cells. We found filopodia-like protrusions enriched at damage sites and acting as scaffolds for shedding, which involves F-actin dynamics, myosin-1a, and vacuolar protein sorting 4B (a component of the ‘endosomal sorting complex required for transport’ machinery). Overall, shedding is more complex than current models of vesiculation from flat membranes. Its similarities to constitutive shedding in enterocytes argue for a conserved mechanism. Our workflow can also be adapted to study other damage response pathways and dynamic cellular events.

scholarly journals Agent-Based Modeling Demonstrates How Local Chemotactic Behavior Can Shape Biofilm Architecture

mSphere ◽  
2019 ◽  
Vol 4 (3) ◽  
Author(s):  
Emily G. Sweeney ◽  
Andrew Nishida ◽  
Alexandra Weston ◽  
Maria S. Bañuelos ◽  
Kristin Potter ◽  
...  
Keyword(s):  
Helicobacter Pylori ◽  
Three Dimensional ◽  
Structural Features ◽  
Agent Based Modeling ◽  
Emergent Properties ◽  
Cellular Interactions ◽  
Biofilm Growth ◽  
Content Type ◽  
Agent Based ◽  
H Pylori

ABSTRACTBacteria are often found living in aggregated multicellular communities known as biofilms. Biofilms are three-dimensional structures that confer distinct physical and biological properties to the collective of cells living within them. We used agent-based modeling to explore whether local cellular interactions were sufficient to give rise to global structural features of biofilms. Specifically, we asked whether chemorepulsion from a self-produced quorum-sensing molecule, autoinducer-2 (AI-2), was sufficient to recapitulate biofilm growth and cellular organization observed for biofilms ofHelicobacter pylori, a common bacterial resident of human stomachs. To carry out this modeling, we modified an existing platform, Individual-based Dynamics of Microbial Communities Simulator (iDynoMiCS), to incorporate three-dimensional chemotaxis, planktonic cells that could join or leave the biofilm structure, and cellular production of AI-2. We simulated biofilm growth of previously characterizedH. pyloristrains with various AI-2 production and sensing capacities. Using biologically plausible parameters, we were able to recapitulate both the variation in biofilm mass and cellular distributions observed with these strains. Specifically, the strains that were competent to chemotax away from AI-2 produced smaller and more heterogeneously spaced biofilms, whereas the AI-2 chemotaxis-defective strains produced larger and more homogeneously spaced biofilms. The model also provided new insights into the cellular demographics contributing to the biofilm patterning of each strain. Our analysis supports the idea that cellular interactions at small spatial and temporal scales are sufficient to give rise to larger-scale emergent properties of biofilms.IMPORTANCEMost bacteria exist in aggregated, three-dimensional structures called biofilms. Although biofilms play important ecological roles in natural and engineered settings, they can also pose societal problems, for example, when they grow in plumbing systems or on medical implants. Understanding the processes that promote the growth and disassembly of biofilms could lead to better strategies to manage these structures. We had previously shown thatHelicobacter pyloribacteria are repulsed by high concentrations of a self-produced molecule, AI-2, and thatH. pylorimutants deficient in AI-2 sensing form larger and more homogeneously spaced biofilms. Here, we used computer simulations of biofilm formation to show that localH. pyloribehavior of repulsion from high AI-2 could explain the overall architecture ofH. pyloribiofilms. Our findings demonstrate that it is possible to change global biofilm organization by manipulating local cell behaviors, which suggests that simple strategies targeting cells at local scales could be useful for controlling biofilms in industrial and medical settings.

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