Related Experiment Videos
Electron microscope observations on the effects of polymixin B sulfate on cell walls of Chlamydia psittaci
Abstract:
The effects of polymixin B sulfate on cell walls of mature elementary body (EB) and of immature developmental reticulate body (RB) of Chlamydia psittaci were investigated. When purified EB were treated with polymixin (10(4) units per ml or more) at 37 C for 60 min, about 70% of EB was found to be covered with a number of projections. Further incubation did not increase the percentage affected. The infectivity after treatment as assayed by the inclusion counting technique was reduced by 70% of the original titer. These results suggest that EB with the projections are no longer infective. The projections had obscure outlines and were 20 to 40 nm in diameter when seen in thin sections. In the negatively stained preparations, the projections were composed of aggregations of fine particles 4 to 5 nm in diameter. Treatment with sodium dodecyl sulfate at the same concentration used for cell wall isolation removed the projections completely, and the cell walls were converted to rather ragged forms apparently composed of outside and inside layers. When RB cell walls prepared from infected cells at 18 hr after infection were treated with polymixin at the same concentration, the projections having the same morphology with those seen on treated EB cell walls were observed only on the inside surface of cell wall.
Insights
Polymixin B sulfate treatment induced projections on Chlamydia psittaci elementary bodies (EB), reducing infectivity by 70%. These projections suggest a mechanism for polymixin B
Area of Science:
- Microbiology
- Cell Biology
- Infectious Diseases
Background:
- Chlamydia psittaci is an obligate intracellular bacterium.
- Understanding the effects of antibiotics on bacterial cell walls is crucial for developing new treatments.
Purpose of the Study:
- To investigate the effects of polymixin B sulfate on the cell walls of Chlamydia psittaci elementary bodies (EB) and reticulate bodies (RB).
- To determine if polymixin B sulfate treatment affects the infectivity of EB.
Main Methods:
- Purified EB and RB cell walls were treated with polymixin B sulfate.
- Electron microscopy (thin sections and negative staining) was used to visualize cell wall changes.
- Infectivity assays (inclusion counting technique) were performed on treated EB.
Main Results:
- Polymixin B sulfate treatment induced projections on approximately 70% of EB.
- EB treated with polymixin B sulfate showed a 70% reduction in infectivity.
- Projections on EB were 20-40 nm in diameter and composed of 4-5 nm particles.
- Sodium dodecyl sulfate removed projections, revealing ragged cell wall layers.
- RB cell walls showed similar projections on the inner surface after polymixin B sulfate treatment.
Conclusions:
- Polymixin B sulfate induces significant morphological changes in Chlamydia psittaci EB cell walls.
- The formation of these projections is associated with a loss of EB infectivity.
- These findings provide insights into the mechanism of polymixin B sulfate action against Chlamydia psittaci.