Question

What happens during transformation in Pneumococcus bacteria?

Answer 1

Transforming principle of Griffith:

1. During the experiment, Griffith cultured Streptococcus pneumoniae bacteria that showed two patterns of growth.
2. One was a culture plate, that consisted of smooth shiny colonies (S) whereas the other consisted of rough colonies (R).
3. The difference was due to the presence of mucous coat in S strain bacteria, and the R strain bacteria lacked them.

Experiment: Griffith injected S(Smooth) and R(Rough) strains into the mice.

1. The one that was infected with the S strain developed pneumonia and then died whereas the one infected with the R strain stayed alive.
2. In the second stage, Griffith first heat-killed the S strain bacteria and then injected them into the mice, but the mice stayed alive.
3. Then, he later mixed the heat-killed S and live R strains. This mixture was then injected into mice and they died. In addition to this, he found living S strain bacteria in dead mice.

Conclusion:

1. Based on his observations, Griffith concluded that R strain bacteria had been transformed by the S strain bacteria.
2. The R strain inherited some ‘transforming principle’ from the heat-killed S strain bacteria that possibly made them virulent.
3. And he assumed this transforming principle as their genetic material.