Frederick griffith experiment year

British bacteriologist (1877–1941)

For other people named Frederick Griffith, see Frederick Griffith (disambiguation).

Frederick Griffith (1877–1941) was a British bacteriologist whose focus was the epidemiology and pathology of bacterial pneumonia. In January 1928 he reported what is now known as Griffith's experiment, the first widely accepted demonstrations of bacterial transformation, whereby a bacterium distinctly changes its form and function.

He showed that Streptococcus pneumoniae, implicated in many cases of lobar pneumonia, could transform from one strain into a different strain. The observation was attributed to an unidentified underlying principle, later known in the Avery laboratory as the "transforming principle" (abbreviated as T. P.) and identified as DNA. America's leading pneumococcal researcher, Oswald T. Avery, speculated that Griffith had failed to apply adequate controls. A cautious and thorough researcher, and a reticent individual, Griffith's tendency was to publish only findings that he believed truly significant, and Griffith's findings were rapidly confirmed by researchers in Avery's laboratory. His discovery was one of the first to show the central role of DNA in heredity.

Early life

Frederick Griffith was born in Prescot, Merseyside (formerly in Lancashire) England, in late 1877 (Registered December quarter in Prescot, Lancashire registration district, vol 8b, page 670), and attended Liverpool University. Thereafter, he worked at the Liverpool Royal Infirmary, the Joseph Tie Laboratory, and the Royal Commission on Tuberculosis. In 1910 Fred Griffith was hired by the local government board.

Ministry of Health office

During World War I (1914–18), the local government board's laboratory was assumed by the national government, namely UK government, and became the Ministry of Health's Pa

It may come as a surprise that less than a century ago, even the most educated members of the scientific community were unaware that DNA was a hereditary material. Frederick Griffith conducted a series of experiments with Streptococcus pneumonia bacteria and mice in 1928 and concluded that the R-strain bacteria must have picked up a "transforming principle" from the heat-killed S bacteria, allowing them to "transform" into smooth-coated bacteria and become virulent.

In this article, we'll look at one of the classic experiments that led to the discovery of DNA as a genetic information carrier.

Who was Frederick Griffith?

• The "Griffith's Experiment," carried out by English bacteriologist Frederick Griffith in 1928, described the transformation of a non-pathogenic pneumococcal bacteria into a virulent strain.

• Griffith combined living non-virulent bacteria with a heat-inactivated virulent form in this experiment.

• He was the first to discover the "transforming principle," which led to the discovery of DNA as a carrier of genetic information.

• He suggested that bacteria can transfer genetic information via a process known as transformation.

• Griffith's goal was not to identify the genetic material but to create a vaccine against pneumonia. In his experiments, Griffith used two related strains of bacteria known as R and S.

• Griffith's work was expanded by Avery, MacLeod, and McCarty.

R Strain And S Strain Bacteria

• Streptococcus pneumonia comes in several types or strains. Griffith chose two different strains for his experiment.

• One strain of bacteria has smooth surfaces and is known as the smooth strain (S strain), while the other has rough surfaces and is known as the rough strain (R strain).

• Bacteria of the S strain have smooth surfaces because they produce a polysaccharide protective coating that forms the outermost layer.

• Apart from the morphological differences, Griffith discovered another significant difference between the S and

Griffith’s Experiment

In 1928, Frederick Griffith conducted one of the first experiments to show that cells possessed genetic material

Griffith's experiment involved the use of two strains of pneumococcus – a deadly virulent strain (S) or a non-virulent strain (R)

• When Griffith infected mice with the non-virulent bacteria (strain R), the mice survived
• When Griffith infected mice with the virulent bacteria (strain S), the mice died
• When Griffith infected mice with heat-killed virulent bacteria (strain R), the mice survived as the bacteria had been killed
• When Griffith infected mice with a mix of heat-killed strain S and living strain R, the mice were found to have died

From this Griffith’s concluded that the living R cells had somehow been transformed into virulent S cells

• This indicated that there was some form of transferrable genetic material present within the cells (i.e. DNA)

Griffith’s Experiment – Demonstrating Bacterial Transformation

Avery-MacLeod-McCarty Experiment

Oswald Avery and colleagues expanded upon the findings of Frederick Griffith to demonstrate that DNA is the genetic material

• They prepared cultures containing the heat-killed S strain and then removed lipids and carbohydrates from the solution
• Next they treated the solutions with different digestive enzymes (DNase, RNase or protease) to destroy the targeted compound
• Finally, they introduced living R strain cells to the culture to see which cultures would develop transformed S strain bacteria

Only in the culture treated with DNase did the S strain bacteria fail to grow (i.e. no DNA = no transformation)

• This indicated that DNA was the genetic component that was being transferred between cells

Despite this finding, the scientific community was reluctant to accept the role of DNA as a genetic material

• It was only 8 years later, when Hershey and Chase conducted their experiment, that the concept gained tractio

Experiment demonstrating transfer of genetic information

Griffith's experiment, performed by Frederick Griffith and reported in 1928, was the first experiment suggesting that bacteria are capable of transferring genetic information through a process known as transformation. Griffith's findings were followed by research in the late 1930s and early 40s that isolated DNA as the material that communicated this genetic information.

Pneumonia was a serious cause of death in the wake of the post-WWI Spanish influenza pandemic, and Griffith was studying the possibility of creating a vaccine. Griffith used two strains of pneumococcus (Diplococcus pneumoniae) bacteria which infect mice – a type III-S (smooth) which was virulent, and a type II-R (rough) strain which was nonvirulent. The III-S strain synthesized a polysaccharide capsule that protected itself from the host's immune system, resulting in the death of the host, while the II-R strain did not have that protective capsule and was defeated by the host's immune system. A German bacteriologist, Fred Neufeld, had discovered the three pneumococcal types (Types I, II, and III) and discovered the quellung reaction to identify them in vitro. Until Griffith's experiment, bacteriologists believed that the types were fixed and unchangeable, from one generation to another.

In this experiment, bacteria from the III-S strain were killed by heat, and their remains were added to II-R strain bacteria. While neither alone harmed the mice, the combination was able to kill its host. Griffith was also able to isolate both live II-R and live III-S strains of pneumococcus from the blood of these dead mice. Griffith concluded that the type II-R had been "transformed" into the lethal III-S strain by a "transforming principle" that was somehow part of the dead III-S strain bacteria.

Scientific advances since then have revealed that the "