Frederick Griffith was born in 1881, died in 1941. He was a bacteriologist who discovered that if he put pathogenic (disease-causing) pneumococcus bacteria which had been killed by heat in with nonpathogenic pneumococcus bacteria which were alive, then the live, nonpathogenic bacteria would become pathogenic. His work became the groundwork for other scientists to discover that DNA was the factor which transformed the bacteria.
WordNet Dictionary