Obtaining pure phage stock
Transfer phages from the clearing zone on the plate to 1 mL phage buffer or sterile sea water in a sterile tube by scraping off the surface layer of the soft agar containing the phages using a sterile loop .
Allow the phages to diffuse into the medium overnight at 4°C .
Vortex the tube and centrifuge the sample ( 10,000 x g , 10 min ) to remove bacteria and agar .
Transfer the supernatant to a new tube .
This sample will typically contain 106–108 phages mL–1 .
To isolate single phages , dilutions of this concentrate should be done , followed by plaque assay , and subsequent isolation of phages from single plaques .
Usually , this procedure is repeated 3 times to dilute out any contaminant phage associated with the phage of interest and increase the probability that only one specific phage is present in the final phage stock .
In the end , the phage concentrate is 0.2 µm filtered and kept in the fridge .
