Mgso4 x 7 h2o

Water from all sampling sites was filtered through a 0.2 µm pore size PES syringe filter and the flow-through collected for phage isolation using plaque assay following Nilsson et al. [53 (link)]. Briefly, 500 µl of the water sample was mixed with 3.5 ml top agar (450 mM NaCl (Sigma), 50 mM MgSO₄ x 7 H₂O (Sigma), 50 mM Trizma base (Sigma), 5 g l⁻¹ low-melting agarose (Thermo Scientific, Waltham, MA, USA)) and 300 µl overnight bacterial culture of Alishewanella sp. SMS8 or Pseudoalteromonas tunicata SMS2 (Table S2a). Plates were incubated on the bench overnight, and plaque-forming units were monitored over 48 h. Plaques of different size and morphologies were picked from plates using a sterile 100 µl pipet tip and stored in MSM buffer ( = top-agar without low-melting agarose) at 4 °C. Phages were purified by replating thrice before two fully lysed plates per viruses were harvested with 5 ml MSM buffer. The phage-MSM mixture was centrifuged at 3260 × g for 20 min, and the supernatant was filtered through a 0.2 µm pore size syringe filter and stored at 4 °C. The phages were stored both as free phages at 4 °C and in infected hosts at −80 °C. For infected hosts, the 400 µl freshly harvested phage stock was mixed with 1.2 ml overnight bacterial culture for 15 min before being mixed with glycerol and frozen as described above.

Bovine Serum Albumin, fluorescein isothiocyanate-dextran (wt 4,000), dimethyl-sulfoxide (DMSO), Bradford reagent, Cell Lytic-M, lipopolysaccharide from Escherichia coli, hydroxytyrosol, tyrosol, NaCl, NaF, K₂HPO₄, KH₂PO₄, MgSO₄x7H₂O, CaCl₂x6H₂O, NaHCO₃, Tween 80 and all solvents of analytical grade were purchased from Sigma Aldrich (Milano, Italy). tyrosol glucuronide, tyrosol sulfate sodium salt, 3′- hydroxytyrosol 3′-glucuronide, hydroxytyrosol 3-sulfate sodium salt, were obtained from LGC standards (Sesto San Giovanni, Italy). The Phosphatase and Protease Inhibitor Cocktail, nitrocellulose membranes, gels and all material for electrophoresis were purchased from ThermoFisher Scientific (Massachusetts, United States). ReagentPack Subculture Reagents with Trypsin/EDTA, TNS (Trypsin Neutralizer solution) and HEPES (2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acid) solutions were obtained from Lonza (Basel, Switzerland). Transwell inserts were obtained from Corning Costar Corp. (New York, N.Y., United States).