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Electron microscopy of cell cultures infected with a chlamydial agent causing polyarthritis of lambs
1The National Animal Disease Laboratory, Animal Disease and Parasite Research Division, Ames, Iowa 50010.
Abstract:
McCoy cell cultures infected with the agent of ovine chlamydial polyarthritis were examined with the electron microscope. The agent was seen as small dense particles (250 to 450 nm) with an eccentric nucleoid and a multilaminated cell wall, as large (800 to 1,200 nm) granular particles surrounded by two unit membranes and as intermediate particles. Replication, which occurred throughout the cytoplasm, was initiated by phagocytosis of a small dense particle and terminated by rupture of the plasma membrane. Upon entering a cell, the small dense particles developed into large granular particles which divided by binary fission. Daughter particles either repeated the division or condensed to form new small dense particles.
Insights
The agent causing ovine chlamydial polyarthritis replicates within McCoy cells. Electron microscopy revealed its distinct developmental cycle, from small dense particles to large granular forms, culminating in cell lysis.
Area of Science:
- Microbiology
- Veterinary Pathology
- Cell Biology
Background:
- Ovine chlamydial polyarthritis is a significant disease in sheep.
- The causative agent's ultrastructure and replication cycle were previously poorly understood.
Purpose of the Study:
- To elucidate the ultrastructural morphology of the ovine chlamydial polyarthritis agent.
- To describe the replication process within McCoy cell cultures.
Main Methods:
- McCoy cell cultures were infected with the ovine chlamydial polyarthritis agent.
- Infected cells were examined using transmission electron microscopy.
Main Results:
- The agent exhibited pleomorphism, appearing as small dense particles (250-450 nm), large granular particles (800-1200 nm), and intermediate forms.
- Replication occurred in the cytoplasm, initiated by phagocytosis of small dense particles.
- Replication involved development into large granular particles, binary fission, and eventual cell lysis.
Conclusions:
- The study details the morphological forms and intracellular replication cycle of the ovine chlamydial polyarthritis agent.
- Understanding this cycle is crucial for developing effective control strategies against the disease.
