Pseudomonas aeruginosa Strategies in Infections and Intraspecies Competition
| dc.contributor.advisor | Kirienko, Natasha V | en_US |
| dc.contributor.advisor | Grande-Allen, Jane | en_US |
| dc.creator | Xu, Qi | en_US |
| dc.date.accessioned | 2025-01-16T20:18:40Z | en_US |
| dc.date.available | 2025-01-16T20:18:40Z | en_US |
| dc.date.created | 2024-12 | en_US |
| dc.date.issued | 2024-12-03 | en_US |
| dc.date.submitted | December 2024 | en_US |
| dc.date.updated | 2025-01-16T20:18:40Z | en_US |
| dc.description.abstract | Pseudomonas aeruginosa is a Gram-negative, opportunistic human pathogen responsible for a variety of nosocomial infections, including bloodstream infections, ventilator-associated pneumonia, and urinary tract infections. These infections pose significant challenges in healthcare settings due to P. aeruginosa’s ability to gradually develop resistance to a wide range of antibiotics, including β-lactams, aminoglycosides, and fluoroquinolones. Consequently, understanding the mechanisms of P. aeruginosa infections is crucial for developing new modalities treatments, such as antivirulence therapy. A key aspect of its pathogenicity lies in the production of numerous virulence factors, including exotoxins, proteases, and quorum-sensing molecules, which enable it to damage host tissues and evade the immune system. Additionally, P. aeruginosa exhibits a remarkable ability to adapt to polymicrobial environments, often outcompeting other microorganisms by utilizing several secretion systems or quorum sensing systems to gain a fitness advantage. This adaptability not only enhances its survival but also makes it a formidable pathogen in chronic infections, particularly in immunocompromised patients. Here we demonstrated that a class of glycolipids called rhamnolipids predominantly drive P. aeruginosa acute virulence against murine macrophages. Secreted rhamnolipids can form micelles that exhibit acute cytotoxicity, rupturing the macrophage plasma membrane and damaging intracellular organellar membranes within minutes. We also examine these rhamnolipid micelles’ structural and biochemical properties via transmission electron microscopy and liquid chromatography-mass spectrometry. While these micelles are particularly toxic to macrophages, they are also capable of damaging a wide range of other cells, including human bronchial epithelial cells, red blood cells, and even Gram-positive bacteria. Finally, we reported that rhamnolipid production in various panels of clinical isolates strongly correlates with P. aeruginosa virulence. In addition, we also examined the consequences of pyoverdine production during P. aeruginosa lung infection, using an adapted in vitro pyoverdine virulence model in human bronchial epithelial cells (16HBE). Conditioned medium from P. aeruginosa caused acute cell death and severe damage to the epithelial monolayer in a pyoverdine-, but not pyochelin-, dependent manner. Interestingly, pyoverdine production is associated with secretion of cytotoxic rhamnolipids. Consistent with this observation, chemical depletion of lipids or genetic disruption of rhamnolipid production was sufficient to abrogate toxicity from conditioned medium on 16HBE cells. Altogether, these findings suggest that pyoverdine and pyochelin play distinct roles in virulence during acute P. aeruginosa lung infections. In terms of intraspecies competition strategies employed by P. aeruginosa, we used a genome-wide transposon insertion library screen to discover that ST111 strains outcompete multiple non-ST111 strains through production of R pyocin. We confirmed this finding by showing that competitive dominance in vitro was lost by ST111 mutants with R pyocin gene deletions. Further investigation showed that sensitivity to ST111 R pyocins (specifically R5 pyocin) and R1 pyocins is caused by deficiency in the O-antigen ligase waaL, which leaves lipopolysaccharide (LPS) bereft of O antigen, enabling pyocins to bind the LPS core. Analysis of 5,135 typed P. aeruginosa strains revealed that majority of international, high-risk sequence types (including ST111, ST175, and ST235) are enriched for R5 pyocin production, indicating a correlation between these phenotypes and suggesting a novel approach for evaluating risk from emerging prevalent P. aeruginosa strains. Overall, our study sheds light on the mechanisms underlying the dominance of ST111 strains, highlighting the role of waaL in R pyocin susceptibility. | en_US |
| dc.format.mimetype | application/pdf | en_US |
| dc.identifier.uri | https://hdl.handle.net/1911/118191 | en_US |
| dc.language.iso | en | en_US |
| dc.subject | Pseudomonas aeruginosa | en_US |
| dc.subject | infection | en_US |
| dc.subject | intraspecies competition | en_US |
| dc.title | Pseudomonas aeruginosa Strategies in Infections and Intraspecies Competition | en_US |
| dc.type | Thesis | en_US |
| dc.type.material | Text | en_US |
| thesis.degree.department | Bioengineering | en_US |
| thesis.degree.discipline | Bioengineering | en_US |
| thesis.degree.grantor | Rice University | en_US |
| thesis.degree.level | Doctoral | en_US |
| thesis.degree.name | Doctor of Philosophy | en_US |
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