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Expression of pili and capsule by the avian strain P-1059 of Pasteurella multocida
P A Rebers1, A E Jensen, G A Laird
1U.S. Department of Agriculture, National Animal Disease Center, Ames, Iowa 50010.
Abstract:
The avian strain P-1059 of Pasteurella multocida was grown on blood agar (BA), on dextrose-starch agar (DSA), or in Heddleston's hydrogen sulfide test broth. Cells were examined for the presence of pili using electron microscopy after staining with phosphotungstic acid, and they were examined for capsule after ruthenium red staining. Pili were found on the capsulated iridescent type, P-1059I, and on two non-capsulated variants, the blue, P-1059B, and the gray, P-1059G. Many cells grown on BA were heavily piliated. In contrast, fewer cells grown on DSA had pili, and piliation was only slight to moderate. The P-1059I, P-1059B, and P-1059G produced pellicles when grown on broth medium. Pili were found on the circumference of the cells grown on either agar or broth medium. Occasionally a pilus connecting two cells was seen on cells cultured in broth. Cultivation of the P-1059I on DSA containing the iron-chelating agent alpha,alpha'-bipyridyl produced a non-capsulated blue variant. The non-capsulated variant reverted to P-1059I when grown on BA but did not revert when grown on DSA.
Insights
Pili presence in Pasteurella multocida varied with growth medium. Blood agar promoted heavy piliation, while dextrose-starch agar resulted in less pili, impacting bacterial morphology and variant development.
Area of Science:
- Microbiology
- Bacteriology
- Electron Microscopy
Background:
- Pasteurella multocida is an important avian pathogen.
- Pili are surface appendages involved in bacterial adhesion and colonization.
- Understanding factors influencing pili expression is crucial for controlling infections.
Purpose of the Study:
- To investigate the effect of different growth media on pili production in avian Pasteurella multocida strain P-1059.
- To characterize the relationship between capsular status, pili expression, and colony morphology.
- To explore the role of iron availability in regulating capsular and pilus formation.
Main Methods:
- Cultivation of Pasteurella multocida P-1059 on blood agar, dextrose-starch agar, and in broth.
- Electron microscopy with phosphotungstic acid staining for pili visualization.
- Ruthenium red staining for capsule detection.
- Cultivation with alpha,alpha'-bipyridyl to assess iron's role.
Main Results:
- Pili were observed on capsulated (P-1059I) and non-capsulated (P-1059B, P-1059G) variants.
- Blood agar supported heavy piliation, whereas dextrose-starch agar showed reduced pili.
- Pili were located on the cell circumference, with occasional intercellular connections in broth.
- Iron chelation induced a non-capsulated variant, which reverted on blood agar but not dextrose-starch agar.
Conclusions:
- Growth medium significantly influences pili expression in Pasteurella multocida.
- Pili are present in both capsulated and non-capsulated forms of the P-1059 strain.
- Environmental factors, like iron availability, can modulate bacterial surface structures and reversibility of phenotypic changes.