Streptococcus pneumoniae :
S - Strain (virulent) injected into mice ---> mice die
R - strain injected into mice --> mice alive
S - strain (heat killed) injected into mice ---> mice alive
R - strain (alive) + S (heat killed) strain inject into mice ---> mice die
As the R strain (non-virulent) picked up genetic material from S strain (virulent) and get transformed.
Detailed Answer:
Griffith's experiment : Griffith used mice and Streptococcus pneumoniae for his experiment.
Streptococcus pneumoniae has two strains:
(i) Smooth (S) strain (Virulent) : It has polysaccharide mucus coat and can cause pneumonia.
(ii) Rough (R) strain (Non-virulent): It has no mucous coat and are therefore do not cause pneumonia.
To test fol the trait of pathogenicity, Griffith injected mice with mixes of the two strains :
S - Strain (virulent) injected into mice ---> mice die
R - strain injected into mice --> mice alive
S - strain (heat killed) injected into mice ---> mice alive
R - strain (alive) + S (heat killed) strain inject into mice ---> mice die
He concluded that some 'transforming principle', transferred from heat-killed S-strain to R-strain. It enabled R-strain to synthesize smooth polysaccharide coat and become virulent. This trust be due to the transfer of some genetic material.
