Question

Application Based Questions:
Study the flow chart given below and answer the questions that follow
(a) S-strain → into mice - mice die
(b) R-strain → into mice - mice live
(c) Heat-killed S-strain + live R-strain → into mice → A
(d) Heat-killed S-strain + DNase + live R-strain → into mice → B
Name the organism and differentiate between its two strains R and S respectively.

Answer 1

Hint:When trying to create a pneumonia vaccine, Frederick Griffith inadvertently discovered a transformation. He injected S-strain and/or R-strain pneumococcus bacteria (Streptococcus pneumoniae) samples into mice.

Complete answer:
Some develop smooth shiny colonies (S) when Streptococcus pneumoniae (pneumococcus) bacteria are grown on a culture plate, while others produce rough colonies (R). This is because there is a mucous (polysaccharide) coat of the S strain bacteria, whereas there is no R strain. Mice infected with the S strain (virulent) diet pneumonia infection do not develop pneumonia, but mice infected with the R strain do not.
Mice died when S Strain was injected into mice.
Mice were alive when the R strain was injected into mice.
By heating them, Griffith was able to destroy bacteria. He found that they were not destroyed by heat-killed S strain bacteria injected into mice. The mice died when he injected a combination of heat-killed S and live R bacteria. In addition, from the dead mice, he rescued live bacteria.
Mice were alive when S Strain was injected into mice
Mice live R strain (live) found when S strain (heat-killed) was injected into mice.
He concluded that the heat-killed S strain bacteria had somehow been transformed by the R strain bacteria. Transferred from the heat-killed S pressure, some 'transforming theory' had occurred.
The R strain has caused a smooth polysaccharide coat to synthesize and become virulent. This may be due to genetic material transfer.
Diplococcus pneumoniae (pneumococcus); the S-strain is virulent and capsulated, while the R-strain is non-virulent.

Note: Frederick Griffith concluded that heat-killed S-strain bacteria are present. A chemical triggered the transformation of certain R-strain bacteria into virulent. A material referred to as the transforming theory. But he did not describe the biochemical character of the genetic material.