Related Experiment Videos
In vitro model of adhesion and invasion by Bacillus piliformis
C L Franklin1, D A Kinden, P L Stogsdill
1Department of Veterinary Pathology, College of Veterinary Medicine, University of Missouri, Columbia, Missouri 65211.
Abstract:
An in vitro model of Bacillus piliformis infection was developed to investigate the mechanisms of adhesion and internalization of this obligate intracellular bacterium. Adhesion and internalization events were examined by electron microscopic evaluation of infected Caco-2 cell monolayers. A few bacteria were identified in apical surface invaginations and in vacuoles subjacent to the apical surface, whereas the majority of bacteria were observed free within the cytoplasm, suggesting that B. piliformis entered epithelial cells via a phagocytic process and rapidly escaped the phagosome. To confirm that host cell phagocytosis was involved in entry of B. piliformis into mammalian cells, Intestine 407 cells were treated with the phagocytic inhibitor cytochalasin D, infected with B. piliformis, and evaluated for bacterial internalization by double-fluorescence labeling. The results showed decreased intracellular bacteria, suggesting that internalization was dependent on host cell microfilament function. To examine the role of B. piliformis in internalization, growth of live and Formalin-killed bacteria was compared. Dead bacteria were not internalized, suggesting that B. piliformis actively participates in internalization. B. piliformis appears to enter host cells by a bacterially directed phagocytic process. The in vitro system described should prove invaluable in further investigations of B. piliformis pathogenic mechanisms.
Insights
Bacillus piliformis, an intracellular bacterium, enters host cells through a bacterially directed phagocytic process. This study developed an in vitro model to investigate its adhesion and internalization mechanisms.
Area of Science:
- Microbiology
- Cell Biology
- Infectious Diseases
Background:
- Bacillus piliformis is an obligate intracellular bacterium.
- Understanding its entry mechanisms into host cells is crucial for studying its pathogenesis.
Purpose of the Study:
- To develop an in vitro model to investigate the adhesion and internalization mechanisms of Bacillus piliformis.
- To elucidate the role of host cell machinery and bacterial factors in B. piliformis entry.
Main Methods:
- Developed an in vitro model using Caco-2 and Intestine 407 cell lines.
- Utilized electron microscopy to observe bacterial-host cell interactions.
- Employed cytochalasin D to inhibit host cell phagocytosis.
- Compared internalization of live and Formalin-killed B. piliformis.
Main Results:
- Bacillus piliformis was observed free within the cytoplasm, suggesting rapid phagosome escape.
- Inhibition of host cell phagocytosis (cytochalasin D treatment) decreased bacterial internalization.
- Live bacteria were internalized, while dead bacteria were not, indicating active bacterial participation.
- B. piliformis entry appears to be a bacterially directed phagocytic process.
Conclusions:
- An effective in vitro model for studying Bacillus piliformis infection was established.
- Bacillus piliformis actively engages in its own internalization via a bacterially directed phagocytic mechanism.
- This model provides a valuable tool for future research into B. piliformis pathogenesis.