A domesticated prophage enzyme links bacterial metabolism, episymbiosis and phage fitness

Prophages are increasingly recognized as drivers of bacterial adaptation, yet how domesticated prophage genes shape microbial symbiosis remains poorly understood. Here, we identify GDPDXhp1, a glycerophosphodiester phosphodiesterase encoded by prophage Xhp1 of Schaalia odontolytica XH001, as a metabolic regulator linking bacterial physiology, episymbiosis and phage fitness. Association with the epibiotic bacterium Nanosynbacter lyticus TM7x strongly induced gdpdXhp1 expression and triggered GDPDXhp1-dependent lipid droplet accumulation in XH001. GDPDXhp1 orchestrated glycerophospholipid remodeling, membrane biophysical properties, respiration and cell-surface glycan composition in XH001, thereby promoting TM7x episymbiosis. Remarkably, GDPDXhp1 was also required for productive Xhp1 infection by remodeling susceptible bacterial host envelope structures to facilitate phage-host interactions. Together, our findings reveal a domesticated prophage enzyme that contributes to bacterial metabolism, interspecies symbiosis and viral reproduction, highlighting prophage as an overlooked source of metabolic innovation in microbial symbiosis.