2.4. Phage stability in different environmental conditions
Stability of phage pAh6.2TG at different temperature (4, 25, 30, 35, and 40oC), pH (3, 5, 7, 9 and 11), salinity (0, 5, 10, 20, 40‰), and fish-rearing water (1, 3, 24, and 48 h) were investigated. These tests were carried out by incubating 100 μL of phage culture (approx. 109 PFU/mL) at the respective temperatures, pH, and salinity for 1 and 24 h in 10 mL of SM buffer. All the experiments were conducted in triplicates. The stability of phages in rearing water was performed in duplicates by adding 2 mL of phage pAh6.2TG (approx. 8.5 × 1010 PFU/mL) into 50 L of water (pH = 7.0 ± 1.0, 0% NaCl) containing 20 of Nile tilapia and maintained at 30 ± 1.0 oC. The concentration of viable phages was enumerated by plaque assay (Jun et al., 2013). Phage concentration (logPFU/mL) before incubation in different conditions was set to be 100%.