Within-Host Adaptation Mediated by Intergenic Evolution in Pseudomonas aeruginosa

Area of Science:

• Microbial evolution
• Bacterial pathogenesis
• Genomics and molecular biology

Background:

• Pathogen adaptation to host environments involves genetic mutations.
• Studies have focused on coding regions, neglecting intergenic mutations' role in bacterial evolution.
• The contribution of intergenic mutations to pathogen fitness and host adaptation remains largely unexplored.

Purpose of the Study:

• To investigate the extent and distinct roles of intergenic mutations in Pseudomonas aeruginosa's adaptation to the host environment.
• To identify specific intergenic regions under selection during host adaptation.
• To determine the functional impact of intergenic mutations on gene expression and pathogenic phenotypes.

Main Methods:

• Analysis of intergenic evolution across 44 clonal lineages of Pseudomonas aeruginosa.
• Identification of parallel evolution in specific intergenic regions.
• Genetic and functional characterization of mutations within regulatory elements.

Main Results:

• Identified 77 intergenic regions with parallel evolution in Pseudomonas aeruginosa.
• Found mutations primarily in regulatory elements upstream of transcriptional start sites.
• Demonstrated that intergenic mutations alter gene transcription, affecting phenotypes like antibiotic sensitivity and enabling evolution of essential genes.

Conclusions:

• Intergenic mutations are evolutionarily significant in shaping host-adapted bacterial strains.
• Intergenic and coding regions contribute differently to bacterial adaptation.
• Understanding intergenic evolution is crucial for comprehending pathogen adaptation and developing novel therapeutic strategies.