In the light of Griffith's experiment , explain the action of two strains of Diplococcus pneumoniase and give his conclusion .

Explanation

Explanation of two strains of Diplococcus pneumontae in the light o( Griffith experiment :
( 1) Griffith perfa rmed experiments using a bacterium, Diplococcus pneumoniae which infects mammals with pneumonia.
(2). This bacterium has two strains, viz., 'S' type which is smooth and capsulated and 'R' type which is noncapsulated and rough. 'S' type bacterium is virulent, capable of causing pneumonia if injected into healthy mice. 'R' type bacterium is nonvirulent and does n9t cause infection when injected into healthy mice.
(3) Griffith performed four sets of experiments: .
(i) In first set, he injected mice with 'S' type of bacteria. Here mice developed pneumonia.
(ii) In second set, he injected mice with 'R' type of bacteria. Mice remained healthy as they did not catch infection of pneumonia.
(iii) In third experiment, he injected heat killed 'S' type of bacteria in the mice. Mice in this case remained healthy.
(iv) In fourth experiment, he took the mixture of heat killed 'S' type bacteria and living 'R' type bacteria. He injected this mixture into healthy mice. Mice were infected with. pneumonia and died.
(4) To analyze the results, Griffith collected the blood sample from dead mice. He obtained living 'S' type bacteria after culturing the blood samples.
2. Conclusion of Griffith: (I) Griffith concluded that living 'R' type bacteria picked up virulence from the dead 'S' type bacteria which were present in the mixture. He called this phenomenon as transformation.
(2) The transforming principle present in dead 'S' type bacteria was picked up from the surrounding medium and transformed into the living 'R' bacteria. 'R' type bacteria were able to synthesize a smooth polysaccharide coat or capsule and became virulent. This transforming principle was passed on to the next generations. Hence it was thought to be the genetic material. Later it was found to be DNA.