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Helicobacter pylori produces unique filaments upon host contact in vitro

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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 m 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.

Helicobacter pylori existe sous 2 stades morphologiques distincts : hélicoïde et coccoïde. Les deux stades ont été observés en culture in vitro et dans des biopsies gastriques. Nous avons visualisé H. pylori durant l’infection de cellules AGS par microscopie en immunofluorescence. Du sérum de souris anti-H. pylori ainsi que des sérums humains de patients infectés par H. pylori ont reconnu de longs filaments bactériens minces qui se formaient sur les hélicoïdes et plus fréquemment sur les coccoïdes. Ces filaments atteignaient une longueur de 59 m et reliaient souvent les bactéries. Les anticorps ne réagissaient plus après une oxydation au periodate, ce qui suggère que les hydrates de carbones constituent une composante antigénique importante des filaments. Similairement aux résultats obtenus par microscopie en immunofluorescence, l’imagerie par microscopie électronique à balayage a révélé la présence de structures filamenteuses minces qui étaient absentes des cellules non infectées. La conversion vers le stade coccoïde et le développement des filaments augmentaient en fonction du temps durant l’infection, la formation de filaments atteignant un pic à 4 h. Le nombre de filaments visibles diminuait alors au fur et à mesure de l’agrégation des bactéries à la surface apicale des cellules AGS. Parce que les filaments observés ici sont clairement distincts des autres structures de surface précédemment décrites, incluant les flagelles et le système de sécrétion cag de type IV, nos résultats démontrent que ces filaments représentent un organelle unique encore méconnu.

Document Type: Research Article

Publication date: July 1, 2008

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  • Published since 1954, this monthly journal contains new research in the field of microbiology including applied microbiology and biotechnology; microbial structure and function; fungi and other eucaryotic protists; infection and immunity; microbial ecology; physiology, metabolism and enzymology; and virology, genetics, and molecular biology. It also publishes review articles and notes on an occasional basis, contributed by recognized scientists worldwide.
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