Investigating pneumococcal types
Griffith worked at the British Ministry of Health’s Pathological Laboratory. He studied pneumococcal types in samples from pneumonia patients and compared smooth and rough colony forms. These investigations arose from practical questions about infection and bacterial classification.
The 1928 transformation experiments
In experiments with mice, Griffith mixed living rough bacteria with heat-treated smooth bacteria and subsequently recovered living smooth organisms bearing characteristics of the latter type. His paper examined changes involving several pneumococcal types and demonstrated transformation under experimental conditions.
References: [1]
From a phenomenon to a chemical question
Griffith did not identify DNA in this study. Researchers including Dawson and Sia extended the transformation experiments, while Avery’s programme moved toward extraction and chemical identification of the active material. The 1928 observations supplied the phenomenon that the 1944 DNA-fraction experiments helped explain.
References: [2]