Rapid
Lysis
Method
By
Hershey - In the absence of infection, E. coli bacteria form translucent colonies on agar plates. When the colonies are infected with normal (wild type) T2 bacteriophages (r+), the small plaques formed appear as diffuse turbid haloes with clear centres. Hershey found that lout of 108 or 104 plaques differed from normal plaques in being larger and having sharp edges. These variant plaques were caused by phages called rapid lysis (or) mutants. Rapid lysis mutations located different regions of the viral chromosome have been called rI, rII, etc
