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SummarySome of the variables involved in the production of high titer phage stocks by the agar layer method have been investigated using coli phage T4r as an example. The significant factors have been shown to be the number of virus particles and the number of bacteria inoculated per plate, the length of incubation, the volume of soft agar in the agar layer and the volume of broth used for extraction of the virus from the agar. By an appropriate adjustment of these variable factors it is possible to obtain stocks of the various coli phages of the T series ranging from 1011 to 1012 infectious particles/ml.
Swanstrom et al. (Thu,) studied this question.