Gp8 mediates adsorption of bacteriophage vB_VpP_21JZSM01 to the host Vibrio parahaemolyticus

In this study, we aimed to identify the principal tail protein responsible for mediating adsorption of bacteriophage vB_VpP_21JZSM01 to its host bacterium Vibrio parahaemolyticus, a significant pathogen in aquaculture. The structure and function of three candidate proteins—the tail tubular protein Gp8, tail completion protein Gp20, and tail fibre protein Gp41 — were predicted through bioinformatic analysis. Recombinant plasmids were constructed and the three tail proteins were successfully expressed and purified. Competitive adsorption assays demonstrated an 81.3% reduction in bacteriophage adsorption efficiency following pre-treatment with rGp8, whereas rGp20 and rGp41 showed no statistically significant effects (p > 0.05). Labelling experiments using enhanced green fluorescent protein (EGFP) fusions revealed that only the group treated with rGp8-EGFP exhibited specific fluorescence signals. Furthermore, tight binding of rGp8 to the surface of host bacteria was directly visualised by transmission electron microscopy. Analysis of environmental factors indicated that the adsorption efficiency of rGp8 was optimal at 4 °C (approximately 80%), decreasing to 30% at 75 °C. Neutral pH supported the highest adsorption efficiency (70 – 80%), while strongly acidic (pH ≤ 5) or alkaline (pH ≥ 9) conditions markedly inhibited adsorption, reducing it to below 20%. Our findings identify the tail tubular protein rGp8 as the core functional determinant for host cell adsorption of bacteriophage vB_VpP_21JZSM01, with its adsorption efficiency modulated by temperature and pH.