Related Experiment Videos
Adhesion of Pseudomonas aeruginosa pilin-deficient mutants to mucin
R Ramphal1, L Koo, K S Ishimoto
1Department of Medicine, University of Florida, Gainesville 32610.
Abstract:
Attachment of Pseudomonas aeruginosa to epithelial cells or tracheobronchial mucin is mediated by surface adhesins. Pili, composed of monomeric pilin subunits, make up one such class of adhesins. The formation of pili and flagella in P. aeruginosa is under the control of the alternative sigma factor rpoN. Isogenic mutant strains with insertionally inactivated rpoN genes were constructed with strains PAK, 1244, and CF613 and were tested for their ability to adhere to respiratory mucin. All rpoN mutants showed significant reduction of adherence to mucin relative to that of their wild-type parents. In contrast, the adherence of pilin structural gene mutants was similar to the adherence of wild types. These results provide suggestive evidence that P. aeruginosa also binds to mucin via adhesins that are distinct from pilin and are still under the genetic control of rpoN. Unlike the laboratory strain PAK, the clinical strains 1244 and CF613 are capable of agglutinating erythrocytes. The rpoN mutation had a minimal effect on the interaction of bacteria with erythrocytes, indicating that the transcription of a gene(s) specifying the agglutination phenomenon does not utilize rpoN. These findings collectively indicate the existence of several classes of adhesins on the surface of P. aeruginosa that may play an important role in colonization of the human respiratory tract.
Insights
Pseudomonas aeruginosa uses multiple adhesins for binding to respiratory tract cells. The alternative sigma factor RpoN controls some adhesins, but not erythrocyte agglutination, suggesting diverse colonization mechanisms.
Area of Science:
- Microbiology
- Bacterial Pathogenesis
- Molecular Biology
Background:
- Pseudomonas aeruginosa utilizes surface adhesins for attachment to host cells, including pili composed of pilin subunits.
- The alternative sigma factor RpoN regulates the expression of pili and flagella in P. aeruginosa.
Purpose of the Study:
- To investigate the role of the alternative sigma factor RpoN in the adherence of P. aeruginosa to respiratory mucin.
- To determine if RpoN controls adhesins distinct from pili and flagella.
- To examine the role of RpoN in erythrocyte agglutination by P. aeruginosa.
Main Methods:
- Construction of isogenic rpoN mutant strains of P. aeruginosa (PAK, 1244, CF613).
- Testing the adherence of wild-type and mutant strains to respiratory mucin.
- Assessing the adherence of pilin structural gene mutants to respiratory mucin.
- Evaluating the effect of rpoN mutation on erythrocyte agglutination.
Main Results:
- All rpoN mutants exhibited significantly reduced adherence to respiratory mucin compared to their wild-type counterparts.
- Mutations in pilin structural genes did not affect mucin adherence.
- rpoN mutations had minimal impact on erythrocyte agglutination in clinical strains (1244, CF613).
Conclusions:
- P. aeruginosa employs adhesins distinct from pili, regulated by rpoN, for mucin binding.
- RpoN is not essential for the transcription of genes involved in erythrocyte agglutination.
- Multiple classes of adhesins, under varying genetic control, contribute to P. aeruginosa colonization of the human respiratory tract.