Phage Capsid Morphology Analysis

15 μL of phage lysate was applied to glow-discharged carbon-coated copper grids (Electron Microscopy Sciences; Carbon Film 150 Mesh, Copper) for two minutes before blotting off using a filter paper. The grids were washed three times with distilled water and stained with 2% (w/v) uranyl acetate. Imaging was performed with JEM-1011 electron microscope (JEOL USA, Inc., Peabody, MA, USA) equipped with a digital CDD camera (Model XR50, AMT Imaging, Woburn, MA, USA). All images were captured at 50,000–120,000x magnification. NucleAIzer software^{78 (link)} was used for AI-based automatic segmentation of phage capsids (DNA-filled heads, empty heads or procapsids) to assess potential size differences between them. The automated segmentation picks were manually checked to ensure proper selection of heads/proheads/capsids, and ImageJ v1.54^{79 (link)} was used to measure their areas. Segmentation was done for all images taken at 60,000× magnification.