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Genetically and Phenotypically Distinct Pseudomonas aeruginosa Cystic Fibrosis Isolates Share a Core Proteomic
Anahit Penesyan1, Sheemal S Kumar1, Karthik Kamath1
1Department of Chemistry and Biomolecular Sciences, Faculty of Science and Engineering, Macquarie University, Sydney, New South Wales, Australia.
Abstract:
The opportunistic pathogen Pseudomonas aeruginosa is among the main colonizers of the lungs of cystic fibrosis (CF) patients. We have isolated and sequenced several P. aeruginosa isolates from the sputum of CF patients and compared them with each other and with the model strain PAO1. Phenotypic analysis of CF isolates showed significant variability in colonization and virulence-related traits suggesting different strategies for adaptation to the CF lung. Genomic analysis indicated these strains shared a large set of core genes with the standard laboratory strain PAO1, and identified the genetic basis for some of the observed phenotypic differences. Proteomics revealed that in a conventional laboratory medium PAO1 expressed 827 proteins that were absent in the CF isolates while the CF isolates shared a distinctive signature set of 703 proteins not detected in PAO1. PAO1 expressed many transporters for the uptake of organic nutrients and relatively few biosynthetic pathways. Conversely, the CF isolates expressed a narrower range of transporters and a broader set of metabolic pathways for the biosynthesis of amino acids, carbohydrates, nucleotides and polyamines. The proteomic data suggests that in a common laboratory medium PAO1 may transport a diverse set of "ready-made" nutrients from the rich medium, whereas the CF isolates may only utilize a limited number of nutrients from the medium relying mainly on their own metabolism for synthesis of essential nutrients. These variations indicate significant differences between the metabolism and physiology of P. aeruginosa CF isolates and PAO1 that cannot be detected at the genome level alone. The widening gap between the increasing genomic data and the lack of phenotypic data means that researchers are increasingly reliant on extrapolating from genomic comparisons using experimentally characterized model organisms such as PAO1. While comparative genomics can provide valuable information, our data suggests that such extrapolations may be fraught with peril.
Insights
Pseudomonas aeruginosa isolates from cystic fibrosis (CF) lungs show varied adaptations. Proteomics reveals distinct metabolic strategies compared to the lab strain PAO1, highlighting limitations of genomic data alone for understanding CF lung colonization.
Area of Science:
- Microbiology
- Genomics
- Proteomics
Background:
- Pseudomonas aeruginosa is a key opportunistic pathogen colonizing cystic fibrosis (CF) lungs.
- Understanding P. aeruginosa adaptation in CF lungs is crucial for treatment strategies.
Purpose of the Study:
- To compare P. aeruginosa isolates from CF patients with the model strain PAO1.
- To investigate phenotypic and metabolic differences influencing CF lung adaptation.
- To assess the utility of comparative genomics versus phenotypic data.
Main Methods:
- Isolation and sequencing of P. aeruginosa from CF patient sputum.
- Phenotypic analysis of colonization and virulence traits.
- Genomic comparison with the model strain PAO1.
- Proteomic analysis in a conventional laboratory medium.
Main Results:
- CF isolates exhibited significant phenotypic variability in adaptation to the CF lung.
- Genomic analysis revealed shared core genes but also strain-specific genetic differences.
- Proteomics showed distinct protein expression profiles: PAO1 utilized more nutrient transporters, while CF isolates had broader biosynthetic pathways.
- CF isolates rely more on intrinsic metabolism for nutrient synthesis compared to PAO1's nutrient import.
Conclusions:
- Significant metabolic and physiological differences exist between P. aeruginosa CF isolates and PAO1, not solely detectable by genomics.
- Relying on model organisms like PAO1 for extrapolating genomic data can be misleading.
- Phenotypic and proteomic data are essential for a comprehensive understanding of pathogen adaptation in complex environments like the CF lung.
