The antagonistic coevolution between Pseudomonas sivasensis W-6 and the cold-adapted phage VW6S.

Coevolution is a widespread phenomenon, especially prominent in the dynamic interactions between bacteria and bacteriophages. The continuous antagonistic coevolution, characterized by cycles of bacterial resistance and phage infectivity, drives the diversification of phage adsorption structures and bacterial surface receptors, with significant ecological and evolutionary implications. This study investigated the short-term coevolution (40 days) between Pseudomonas sivasensis W-6 and its cold-adapted phage VW6S, isolated from the Napahai plateau wetland. Genomic resequencing revealed reciprocal adaptations, with mutations occurring in bacterial resistance genes and phage infection-related genes. We identified a putative receptor-binding mechanism wherein the phage-encoded tail fiber protein (gp28) specifically interacts with bacterial surface receptors, mediating host recognition and adsorption. Furthermore, variations in a prophage region during coevolution were found to influence phage adsorption efficiency, indicating that prophage-driven evolutionary changes can affect bacterial survival strategies beyond direct virus-host interactions.