Griffith's Experiment: Bacterial Transformation

This video explains Griffith's experiment to prove the existence of a "transformation principle" via experimentation with mice and two kinds of pneumonia bacteria. His work paved the way for Avery, McCarty and MacLeod to later prove the DNA is the molecule of heredity. Chapters: 0:00-0:06 Introduction 0:06-0:40 S and R Strain of Streptococcus Pneumoniae 0:40-0:58 The Transformation Principle 0:58-1:24 Griffith's Experiment Structure 1:24-1:32 Live R Strain 1:32-1:40 Live S Strain 1:40-2:00 Heat Killed S Strain 2:00-2:30 Heat Killed S Strain, Live R Strain 2:30-2:55 Isolated S Strain 2:55-3:45 Conclusions, Connections to Avery, McCarty and MacLeod's Work Details: While observing the pneumococcus bacteria, Griffith noticed that sometimes the non-virulent R strain would revert into the virulent S strain. He theorized that a “transforming principle” was somehow transferred between the S strain and the R strain, causing the R strain to acquire dangerous properties. To test his theory, he injected five different types of bacteria into groups of mice; 1) Live R strain 2) Live S Strain 3) Heat-Killed S strain 4) a COMBINATION of Heat-killed S strain AND live R-strain 5) S strain that had been isolated from mice in the fourth group. The results Griffith’s famous experiment would confirm the presence of a “transforming principle”. Predictably, the mice from group 1 survived, the mice from group 2 died, and the mice from group 3 survived. However, the mice in group 4 died. On their own, neither the heat killed S strain nor the live R strain should have been deadly, so Griffith concluded that the live R-strain had acquired some type of deadly component from the dead S-strain. He called this mystery component the “transformation principle”. Griffith’s ground-breaking work proved that some organisms can acquire new properties from their environment and from one another, and that non-heritable exchange of genetic information is possible. Useful Sources: https://en.wikipedia.org/wiki/Griffit... https://openstax.org/books/microbiolo... APA Video Citation: [BOGObiology]. (2021, May 24). Griffith's Experiment: Bacterial Transformation. [Video File]. Retrieved from    • Hypertonic, Hypotonic and Isotonic Solutions!