INTRODUCTION
- Streptococcus pneumoniae, commonly known as pneumococcus, is a bacterium that can cause diseases such as pneumonia, meningitis, and otitis media.
- Before Griffith’s experiments, it was thought that the virulence of bacteria was due to the presence of specific proteins or toxins.
- In his initial experiments, Griffith injected mice with two different strains of pneumococcus: a virulent strain and a non-virulent strain.
- The virulent strain was capable of causing disease and death in the mice, while the non-virulent strain did not cause any harm.
- When Griffith injected the virulent strain into mice, the animals became sick and died.
- However, when he injected the non-virulent strain into mice, the animals remained healthy.
- Griffith then boiled the virulent strain of bacteria, which killed the cells and destroyed the proteins and toxins thought to be responsible for virulence.
- When he injected the boiled virulent strain into mice, the animals did not become sick or die.
- However, when Griffith injected a mixture of the boiled virulent strain and the live non-virulent strain, the mice became sick and died.
- Upon further analysis, Griffith discovered that the non-virulent strain had been transformed into a virulent strain, capable of causing disease and death in the mice.
- This transformation was not due to the presence of any protein or toxin but was instead due to the transfer of genetic material from the virulent strain to the non-virulent strain.
- This transfer of genetic material, known as transformation, demonstrated that DNA was the genetic material responsible for the transmission of hereditary information in bacteria.
- Griffith’s experiments laid the groundwork for the discovery of the structure of DNA by Watson and Crick in 1953 and had a significant impact on the development of molecular biology and genetics as scientific disciplines.
