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Demonstration of a capsule on Mycoplasma ovipneumoniae
M Niang1, R F Rosenbusch, J J Andrews
1Department of Microbiology, Immunology and Preventive Medicine, College of Veterinary Medicine, Iowa State University, Ames 50011, USA.
Objective:
To examine Mycoplasma ovipneumoniae for presence of a capsule and its potential role in adherence.
Sample Population:
17 isolates of M ovipneumoniae and 2 isolates of M arginini, recovered from sheep with respiratory tract disease.
Procedure:
Mycoplasmas were cultured in modified Fills broth medium, ovine fetal lung cells, or ovine tracheal ring explants. Pelleted mycoplasmas or ring cultures infected with mycoplasmas were treated with ruthenium red or polycationic ferritin and visualized by transmission electron microscopy. Reactivity of several lectins with the mycoplasmas was studied by use of a microtitration plate agglutination test.
Results:
Electron microscopy revealed a large number of M ovipneumoniae cells covered with an electron dense-stained amorphous material suggesting that it was a capsule. Multiple passages of the microorganisms in modified Friis broth medium decreased thickness of the capsule, but not percentage of cells encapsulated. Marked differences were observed when M ovipeumoniae isolates grown in modified Friis broth medium or co-cultured with ovine fetal lung cells were compared for capsular thickness or percentage of encapsulation. In thin sections of ruthenium red-stained tracheal ring cultures, the mycoplasmas appeared to be in close contact with cilia through their capsule. All isolates of M ovipneumoniae reacted strongly with wheat germ agglutinin lectin.
Conclusions:
Mycoplasma ovipneumoniae produces a polysaccharide capsule with variable thickness that is dependent on culture conditions and strain. Morphologic observations suggest that this capsule facilitates adherence of the organism to ciliated epithelium.
Insights
Mycoplasma ovipneumoniae possesses a capsule that aids its attachment to sheep respiratory tissues. Capsule thickness varies with culture conditions and bacterial strain, impacting adherence.
Area of Science:
- Veterinary Microbiology
- Bacterial Pathogenesis
- Cell Biology
Background:
- Mycoplasma ovipneumoniae is a significant respiratory pathogen in sheep.
- The role of surface structures in mycoplasma adherence is not fully understood.
Purpose of the Study:
- To investigate the presence and characteristics of a capsule in Mycoplasma ovipneumoniae.
- To determine the capsule's potential role in the adherence of M. ovipneumoniae to host cells.
Main Methods:
- Transmission electron microscopy was used to visualize the capsule on M. ovipneumoniae isolates.
- Ruthenium red staining and polycationic ferritin labeling were employed.
- Lectins were used to study surface carbohydrate interactions.
- Cultures were performed in broth, on ovine fetal lung cells, and on tracheal explants.
Main Results:
- Electron microscopy confirmed an electron-dense capsule on M. ovipneumoniae.
- Capsule thickness varied with culture conditions and bacterial strain.
- M. ovipneumoniae showed close contact with ovine tracheal cilia, mediated by the capsule.
- All isolates reacted with wheat germ agglutinin, indicating specific lectin binding.
Conclusions:
- Mycoplasma ovipneumoniae produces a polysaccharide capsule.
- Capsule thickness is influenced by culture environment and bacterial strain.
- The capsule appears to facilitate the adherence of M. ovipneumoniae to ciliated respiratory epithelium.