The Bacteriophage VMY 22 Has Enhanced the Stability of Its Functional Proteins via Adaptive Evolution in a Temperature-Varying Environment

Temperature fluctuations strongly affect microbial viability, often inducing adaptive responses. In this study, we employed the psychrophilic bacterium Bacillus mycoides 41-22 and its associated phage VMY22, originally isolated from the Mingyong Glacier, to investigate phage adaptability under varied temperature conditions. Through selective enrichment at 4 °C, 15 °C, 28 °C, and 32 °C, we observed clear differences in phage infectivity, as assessed by plaque assays, along with genomic mutations and protein structural changes. Notably, mutations predominantly occurred in functional genes (ATPase, endolysin), while the examined structural loci remained conserved. Homology modeling revealed distinct adaptations in protein tertiary structures corresponding to environmental temperatures, suggesting that phage evolution mainly affects post-adsorption processes. Our findings elucidate a novel mechanism of temperature-driven functional protein evolution among cold-adapted bacteriophages (phage) and providing insights into their potential applications in microbial ecology and biotechnology.