Related Experiment Videos
Ultrastructural study of endocytosis of Chlamydia trachomatis by McCoy cells
R L Hodinka1, C H Davis, J Choong
1Department of Microbiology and Immunology, University of North Carolina School of Medicine, Chapel Hill 27514.
Abstract:
The entry of Chlamydia trachomatis into McCoy cells (fibroblasts) was studied by transmission electron microscopy. On adsorption of elementary bodies (EBs) to host cells at 37 degrees C, the EBs were bound primarily to preexisting cell-surface microvilli. They were also observed in coated pits located at the bases of the microvilli and along smooth surfaces of the host cells and were internalized within coated vesicles at this temperature. Postembedding immunogold labeling on Lowicryl thin sections with anti-clathrin antibody as the primary reagent revealed the gold marker localized in pits and vesicles containing chlamydiae. Some EBs were present in smooth-surfaced invaginations at or near the bases of microvilli and in vesicles devoid of distinguishable coat material. A similar entry process was observed with centrifugation-assisted inoculation of EBs onto the McCoy cells. Individual EBs were initially internalized into tightly bound endocytic vesicles. However, within 1 to 3 h postinfection, multiple C. trachomatis EBs were observed in large, loosely bound vesicles. Evidence suggests that vesicles containing C. trachomatis may have fused with one another early in the infectious process. These results indicate that chlamydiae can exploit the specific process of adsorptive endocytosis for entry into host cells and for translocation to a given intracellular destination, which may be different for each species.
Insights
Chlamydia trachomatis elementary bodies (EBs) enter McCoy cells via adsorptive endocytosis, utilizing microvilli and coated pits. This process involves vesicle fusion, facilitating intracellular translocation.
Area of Science:
- Microbiology
- Cell Biology
- Infectious Diseases
Background:
- Chlamydia trachomatis is an obligate intracellular bacterium causing various human infections.
- Understanding the entry mechanism of C. trachomatis into host cells is crucial for developing effective treatments.
Purpose of the Study:
- To investigate the cellular mechanisms by which Chlamydia trachomatis elementary bodies (EBs) enter McCoy cells.
- To elucidate the role of specific cellular structures and processes in C. trachomatis infection.
Main Methods:
- Transmission electron microscopy (TEM) was used to visualize EB entry.
- Postembedding immunogold labeling with anti-clathrin antibody was employed.
- Centrifugation-assisted inoculation was performed to study EB entry.
Main Results:
- EBs adsorbed to and entered McCoy cells via microvilli, coated pits, and coated vesicles.
- Clathrin was localized in pits and vesicles containing EBs, indicating clathrin-mediated endocytosis.
- EBs were also found in smooth invaginations and uncoated vesicles.
- Internalized EBs were initially in tightly bound vesicles, later observed in larger, loosely bound vesicles, suggesting vesicle fusion.
Conclusions:
- Chlamydia trachomatis utilizes adsorptive endocytosis for entry into host cells.
- The entry process involves specific cellular structures like microvilli and clathrin-coated vesicles.
- Vesicle fusion may play a role in the early stages of C. trachomatis infection.