Helicobacter pylori produces unique filaments upon host contact in vitro
Marc Roger Couturier1, Markus Stein
1Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, AB T6G2R3, Canada.
Abstract:
Helicobacter pylori exists in 2 distinct morphological states, helicoid and coccoid. Both have been observed in in vitro culture and in gastric biopsies. We visualized H. pylori during AGS cell infections using immunofluorescence microscopy. Anti-H. pylori mouse serum as well as human serum from H. pylori-positive patients recognized long, thin bacterial filaments, which formed on helicoids and more frequently on coccoids. These filaments reached lengths of 59 microm and often connected bacteria. Periodate oxidation abolished antibody recognition, suggesting that carbohydrates compose a major antigenic component of the filaments. Similar to results obtained using immunofluorescence microscopy, scanning electron microscopy imaging revealed thin filamentous structures, which were absent on uninfected cells. Both coccoid conversion and filament development increased over the time course of infection with peak filament formation at 4 h. The number of visible filaments then decreased as bacteria clustered on the apical surface of AGS cells. Since the observed filaments were clearly distinct from previously described surface structures, including flagella and the cag type IV secretion system, our results demonstrate that these filaments represent a unique, previously unrecognized, organelle.
Insights
Helicobacter pylori forms unique, long filaments during AGS cell infections. These previously unrecognized structures, composed of carbohydrates, connect bacteria and are distinct from flagella or secretion systems.
Area of Science:
- Microbiology
- Cell Biology
- Bacterial Pathogenesis
Background:
- Helicobacter pylori exhibits two main forms: helicoid and coccoid.
- Both morphologies are found in vitro and in patient gastric biopsies.
- Understanding H. pylori's interaction with host cells is crucial for disease research.
Purpose of the Study:
- To investigate the morphological changes of H. pylori during infection of AGS cells.
- To identify and characterize novel structures on H. pylori during host cell interaction.
- To determine the composition and potential function of these structures.
Main Methods:
- Immunofluorescence microscopy using anti-H. pylori antibodies.
- Scanning electron microscopy (SEM) for high-resolution imaging.
- Time-course analysis of bacterial morphology during infection.
- Periodate oxidation to assess filament composition.
Main Results:
- H. pylori formed long, thin filaments (up to 59 microm) during AGS cell infection.
- These filaments were observed on both helicoid and coccoid forms, more frequently on coccoids.
- Filament formation peaked at 4 hours post-infection and decreased as bacteria clustered.
- Periodate oxidation indicated carbohydrates are a major antigenic component of the filaments.
- SEM confirmed the presence of these distinct filamentous structures.
Conclusions:
- H. pylori possesses a previously unrecognized organelle: thin, carbohydrate-rich filaments.
- These filaments are distinct from known bacterial structures like flagella and the cag type IV secretion system.
- Filament formation is dynamic during host cell infection, suggesting a role in bacterial interaction or survival.
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