Webinar: Dr. Clara Torres-Barceló

Date and Time: Tuesday, November 18, 2025, 15:00 CEST.

Abstract

Bacteriophages—viruses that infect bacteria—are key but often overlooked players in plant-associated microbial communities. While commonly explored as potential biocontrol agents, their ecological and evolutionary interactions with bacteria remain poorly understood in plant systems. Addressing this gap can shed light on fundamental processes shaping the plant microbiome and open new avenues for disease management.

In our work, we investigated how phages influence the ecology of bacterial canker disease in apricot trees caused by the Pseudomonas syringae species complex. We first explored the interaction networks between phages isolated from diseased plants and bacterial strains collected from diseased and healthy plant tissues, as well as surrounding environments. Contrary to our expectations, phages frequently infected bacteria regardless of their source, suggesting a few ecological barriers to infection and reflecting the broad distribution of susceptible hosts. We also analysed bacterial genomes to identify prophages and antiviral defence systems, providing insights into how these genomic elements shape bacterial resistance or sensitivity to phage predation.

Complementing this interaction-based approach, we characterised the “phageome” of apricot trees by purifying viral particles and sequencing metagenomes from soil, buds, and twigs of healthy and diseased trees, alongside metabarcoding analyses of P. syringae populations. We detected over 13,000 phage operational taxonomic units (vOTUs), 28% of which could be assigned to bacterial hosts. Soil harboured the highest phage richness, while twigs and buds were comparable but displayed distinct community compositions. Diseased twigs showed a marked increase in Pseudomonas phages and an absence of abundant Actinomycetota and Bacillota phages compared to other niches, suggesting a disease-associated disruption of the normal phage–bacteria equilibrium. This study provides new insights into the role of phages in plant disease, paving the way for novel, ecology-based strategies for disease management.

Speaker Bio: Dr. Clara Torres-Barceló is a researcher at INRAE's Plant Health Institute Montpellier (PHIM), pioneering the use of bacteriophages to manipulate plant-associated microbial communities for crop protection. Her interdisciplinary approach combines evolutionary biology, community ecology, and molecular microbiology to develop phage-based therapeutics against key agricultural pathogens, including Pseudomonas syringae, Erwinia amylovora (fire blight), and Ralstonia solanacearum (bacterial wilt). Her research journey began with a Ph.D. in evolutionary virology at the University of València, followed by postdoctoral work at Oxford University studying antibiotic resistance evolution. She explored phage-antibiotic interactions at the Institute of Evolutionary Sciences of Montpellier (2013-2015) and developed phage biocontrol applications during fieldwork in Reunion and Mauritius Islands (2018).