36 ELEMENTARY BACTERIOLOGY LABORATORY EXERCISES 
EXERCISE 53 
BACTERIOPHAGE 
Bacteriophage is an ultramicroscopic, filterable substance which causes a 
lysis of bacterial cells. 
Put two drops of bacteriophage filtrate on the surface of a four hours’ old 
agar slope culture of Bacterium aerogenes. Drop the filtrate on the top of the 
slope so that it will run down over the bacterial growth. Treat in the same man- 
ner, for a control, another culture with two drops of sterile broth. 
Keep at laboratory temperature and observe during the laboratory period. 
