Phages were suspended in PBS solutions and stored at 4℃. Titration was performed using the protocol described by Łoś et al. . Briefly, immediately before usage 200 μl of bacteria culture was suspended in warm agar and split onto bottom agar containing x-gal and IPTG. Then, 2.5 μl of subsequent 10-fold dilutions of the phage sample were dripped onto the bacteria lawn.