Phage-host coevolution in natural populations

Area of Science:

• Microbiology
• Evolutionary Biology
• Genomics

Background:

• Bacteriophages (phages) and their bacterial hosts engage in continuous coevolution.
• This dynamic involves reciprocal adaptations in resistance and counter-resistance mechanisms.

Purpose of the Study:

• To investigate phage-host evolution in natural populations of Vibrio crassostreae.
• To understand the genetic basis of phage adaptation and bacterial defense systems.

Main Methods:

• Isolation of Vibrio crassostreae strains and vibriophages from an oyster farm over a 5-month period.
• Large-scale cross-infection studies (81,926 pairs) to map host-phage interactions.
• Genomic analysis to identify defense systems and phage adaptation mechanisms.

Main Results:

• A modular host-phage interaction network was identified, demonstrating local adaptation.
• Bacterial defense systems, often on mobile genetic elements, restrict phage propagation.
• Phages adapt to bacterial defenses via epigenetic and genomic modifications, altering host range.

Conclusions:

• Bacterial defense evolution and phage counter-defense are driven by frequent genetic exchanges on mobile genetic elements.
• Local adaptation and modularity characterize phage-host interactions in wild populations.
• Understanding these dynamics is crucial for microbial ecology and phage therapy development.