Griffith's experiment discovering the transforming principle in pneumococcus bacteria. Griffith's experiment, was an experiment done in 1928 by Frederick Griffith. It was one of the first experiments showing that bacteria can get DNA through a process called transformation. Griffith used two strains of Pneumococcus.These bacteria infect mice. He used a type III-S (smooth) and type II-R (rough) strain.The III-S strain covers itself with a polysaccharide capsule that protects it from the host's immune system.This means that the host will die.riffith used two strains of Pneumococcus. These bacteria infect mice. He used a type III-S (smooth) and type II-R (rough) strain. The III-S strain covers itself with a polysaccharide capsule that protects it from the host's immune system. This means that the host will die.