Surprising niche for the plant pathogen Pseudomonas syringae

Area of Science:

• Environmental microbiology
• Plant pathology
• Bacterial ecology

Background:

• Plant pathogenic bacteria are primarily studied in agricultural contexts.
• Human pathogens' environmental niches are well-known, unlike those of plant pathogens.
• Environmental survival traits can inform virulence factors in human pathogens.

Purpose of the Study:

• To investigate non-agricultural niches for plant pathogenic bacteria.
• To explore the ecology and evolution of Pseudomonas syringae outside of agricultural settings.
• To assess the potential of environmental habitats as reservoirs for plant pathogens.

Main Methods:

• Isolation of Pseudomonas syringae from river epilithon in France and the USA.
• Testing of isolated strains for plant pathogenicity and toxin production.
• Sequencing of 16S rDNA to determine genetic lineage and distribution.

Main Results:

• Pseudomonas syringae was isolated from river epilithon at high densities, including pristine environments.
• Isolated strains exhibited functional pathogenicity systems and produced syringomycin-like toxins.
• A widespread genetic lineage of P. syringae was identified across continents, suggesting aerosol/precipitation dispersal.

Conclusions:

• Non-agricultural niches, such as river epilithon, are important for plant pathogenic bacteria ecology and evolution.
• Environmental strains possess traits that could enhance pathogenicity and fitness.
• Limited understanding of these niches hinders comprehension of agricultural epidemics and pathogen evolution.