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Wiesmann, Christina Louise

University of British Columbia

Members of the bacterial genus Pseudomonas form mutualistic, commensal, and pathogenic associations with diverse hosts. The prevalence of host association across the genus suggests that symbiosis may be a conserved ancestral trait and that distinct symbiotic lifestyles may be more recently evolved. Here we show that the metal responsive ColR/S two-component system, part of the Pseudomonas core genome, is functionally conserved between Pseudomonas aeruginosa and Pseudomonas fluorescens. We used a reverse genetics approach, coupled with testing for plant rhizosphere colonization and virulence in a murine abscess model, to show that colR is required for commensalism with plants and virulence in animals. Comparative transcriptomics revealed that the ColR regulon has diverged between P. aeruginosa and P. fluorescens and deleting components of the ColR regulon revealed strain-specific, but not host-specific, requirements for ColR-dependent genes. We also show that colR is likely required for rhizosphere colonization due to sensitivity to metals at the low pH of the rhizosphere. Additionally, we show that homologous ColR-dependent phosphoethanolamine transferase genes predicted to modify the LPS core sugars are not required for zinc tolerance in either P. fluorescens WCS365 or in P. aeruginosa PAO1. Because P. fluorescens WCS365 is a biocontrol strain known for its ability to be protective against pathogens, we additionally tested if ColR and ColR-dependent genes in P. fluorescens are required for pathogen protection. We find that ColR, and a subset of ColR-dependent genes are required for pathogen protection, and that there is partial overlap of the genes required for colonization and protection. Collectively, our results suggest that ColR/S allows Pseudomonas to sense and respond to a host, but that the ColR-regulon has diverged between Pseudomonas strains with distinct lifestyles. Our results additionally show that there is partial conservation of the requirement of ColR-dependent genes in rhizosphere colonization and pathogen protection. Collectively this work suggests that the ColR/S two-component system is broadly required for host association, zinc tolerance, and pathogen protection, but that life-style dependent diversification of the regulon may play a role in host association and lifestyle transitions.

Text

2023-04-20

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/84378

Microbiology and Immunology

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/