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Binary fission of Pneumocystis carinii trophozoites grown in vitro
J D Richardson1, S F Queener, M Bartlett
1Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis 46223.
Abstract:
Trophozoites grown in vitro were shown to undergo binary fission by transmission electron microscopy (TEM). Standard fixation with subsequent embedding in Spurr was employed using 3% glutaraldehyde and 1% osmium tetroxide with 5% sucrose added to both fixatives and 0.1 M cacodylate buffer washes. Trophozoites were grown on WI-38 cells in vitro. Trophozoites were found in various stages of fission. The dividing trophozoite has daughter cells that are rounder than the pleomorphic, non-dividing trophozoites. Tubular forms external to the dividing trophozoites were decreased in number; tubular forms when present were concentrated around the forming septa. Nuclear material was sometimes, but not always, well defined in both daughter cells. There was no concentration of nuclear material at the poles. Vacuoles without membrane were present in the dividing forms. Separate nuclear regions were sometimes found in the dividing trophozoites. These observations suggest that binary fission does occur in culture; however, the significance of binary fission to the life cycle of Pneumocystis carinii (Pc) is not yet clear.
Insights
Pneumocystis carinii trophozoites undergo binary fission in vitro, observed via transmission electron microscopy. Further research is needed to clarify the significance of this asexual reproduction in the Pneumocystis carinii life cycle.
Area of Science:
- Microbiology
- Cell Biology
- Parasitology
Background:
- Pneumocystis carinii is an opportunistic pathogen causing pneumonia in immunocompromised individuals.
- The life cycle and reproductive mechanisms of Pneumocystis carinii have been incompletely understood.
- In vitro cultivation of Pneumocystis carinii has facilitated studies on its biology.
Purpose of the Study:
- To investigate the mode of reproduction of Pneumocystis carinii trophozoites in vitro.
- To characterize the morphological changes during Pneumocystis carinii cell division using transmission electron microscopy.
Main Methods:
- Trophozoites were cultured in vitro on WI-38 cells.
- Standard fixation and embedding techniques were used for transmission electron microscopy (TEM).
- Glutaraldehyde and osmium tetroxide were employed as fixatives, with sucrose and cacodylate buffer.
Main Results:
- Transmission electron microscopy confirmed that Pneumocystis carinii trophozoites undergo binary fission in vitro.
- Dividing trophozoites exhibited rounder daughter cells compared to pleomorphic non-dividing forms.
- Nuclear material distribution and the presence of membrane-less vacuoles were observed during fission.
Conclusions:
- Binary fission is a confirmed mode of asexual reproduction for Pneumocystis carinii in culture.
- The precise role and significance of binary fission in the overall Pneumocystis carinii life cycle require further investigation.
- In vitro studies provide valuable insights into the cellular processes of Pneumocystis carinii.