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Updated: Oct 16, 2026
RNA Isolation of Pseudomonas aeruginosa Colonizing the Murine Gastrointestinal Tract
Published on: September 28, 2011
RpmA is required for nonopsonic phagocytosis of Pseudomonas aeruginosa
1Division of Infectious and Immunological Diseases, Department of Pediatrics, and the Canadian Bacterial Diseases Network, University of British Columbia, Vancouver, British Columbia, Canada V5Z 4H4. dsimpson@cbdn.ca
Abstract:
Pseudomonas aeruginosa causes severe respiratory tract infections in patients with cystic fibrosis (CF). We have been examining nonopsonic phagocytosis of P. aeruginosa by macrophages. To study the P. aeruginosa-macrophage interaction at the molecular level, we have constructed a transposon Tn5G bank in a clinical isolate of P. aeruginosa (strain 4020) and identified mutants resistant to nonopsonic phagocytosis. Phagocytosis-resistant mutants were enriched by passaging the transposon bank over 18 macrophage monolayers. Of 900 individual mutants isolated from this enriched pool in a nonopsonic phagocytosis assay, we identified 85 putative mutants that were resistant to phagocytosis. In this study, we have characterized one of these transposon mutants, P. aeruginosa 4020 H27A, which was poorly ingested. H27A possessed a Tn5G insertion in a gene encoding a protein with homology to the MotA proteins of several species of bacteria. We have called this gene rpmA for required for phagocytosis by macrophages. RpmA is one of two MotA paralogs in P. aeruginosa. This rpmA::Tn5G mutant was motile both on agar plates and in visual examination of wet mounts. The phagocytosis defect was partially complemented by providing the rpmA gene in trans and fully complemented when both rpmA and rpmB were provided. A rpmA null mutant was ingested by macrophages similar to the H27A transposon mutant. These data suggest that the rpmA and rpmB gene products are required for the efficient ingestion of P. aeruginosa by macrophages.
Insights
Pseudomonas aeruginosa requires specific genes, rpmA and rpmB, for macrophages to efficiently engulf the bacteria during respiratory infections. This finding is crucial for understanding bacterial evasion mechanisms in cystic fibrosis patients.
Area of Science:
- Microbiology
- Immunology
- Molecular Biology
Background:
- Pseudomonas aeruginosa is a significant pathogen causing severe respiratory infections, particularly in cystic fibrosis (CF) patients.
- Nonopsonic phagocytosis by macrophages is a key defense mechanism against bacterial pathogens.
- Understanding the molecular basis of bacterial interaction with macrophages is crucial for developing therapeutic strategies.
Purpose of the Study:
- To identify genes in Pseudomonas aeruginosa essential for nonopsonic phagocytosis by macrophages.
- To characterize the role of identified genes in the interaction between P. aeruginosa and macrophages at a molecular level.
Main Methods:
- Construction and screening of a Tn5G transposon mutant bank in P. aeruginosa strain 4020.
- Enrichment of phagocytosis-resistant mutants by serial passage over macrophage monolayers.
- Characterization of a specific mutant (H27A) with a Tn5G insertion in the rpmA gene.
- Complementation studies using in trans expression of rpmA and rpmB genes.
Main Results:
- Identification of 85 putative phagocytosis-resistant mutants from 900 screened.
- Characterization of mutant H27A, showing a Tn5G insertion in rpmA, homologous to bacterial MotA proteins.
- The rpmA::Tn5G mutant exhibited reduced ingestion by macrophages but remained motile.
- Phagocytosis defect was partially complemented by rpmA and fully complemented by both rpmA and rpmB.
Conclusions:
- The rpmA and rpmB gene products are essential for efficient nonopsonic phagocytosis of Pseudomonas aeruginosa by macrophages.
- These findings shed light on bacterial mechanisms for evading host immune defenses.
- Targeting rpmA and rpmB could represent a novel therapeutic approach for P. aeruginosa infections, especially in CF patients.
