Фред Гриффит: Пневмококкты трансформация және ДНК ашуы

British bacteriologist

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, 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. (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.

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 Pathological Laboratory—where Griffith was medical officer. UK government spent money sparingly on the laboratory, which remained very basic, though Griffith and his colleague, William M. Scott, "could do more with a kerosene tin and a primus stove than most men could do with a palace". Griffith performed the pivotal experiments—actually very many experiments—during the 1920s. With outbreak of World War II (1939–45), the laboratory was expanded into the Emergency Public Health Laboratory Service.

Pneumococci has two general forms—rough (R) and smooth (S). The S form is more virulent, and bears a capsule, which is a slippery polysaccharide coat—outside the peptidoglycan cell wall common among all classical bacteria—and prevents efficient phagocytosis by the host's innate immune cells. Injected subcutaneously with S form, mice succumbed to pneumonia and death within several days. However, the R form, lacking a capsule—its outer surface being cell wall—is relatively avirulent, and does not cause pneumonia as often. When Griffith injected heat killed S into mice, as expected, no disease ensued. When mice were injected with a mixture of heat killed S and live R, however, pneumonia and death ensued. The live R had transformed into S—and replicated as such—often characterized as Griffith's Experiment. More accurately, point six of Griffith's abstract reports that R tended to transform into S if a large amount of live R, alone, were injected, and that adding much heat killed S made transformation reliable

Avery's associate Martin Dawson at The Rockefeller Hospital confirmed each of Griffith's reported findings. Even before Griffith's publication, Fred Neufeld had confirmed them as well, and was merely awaiting publication of Griffith's findings before publishing his confirmation. Over the following years, Avery's illness, Graves' disease, kept him much out of his laboratory as other researchers in it experimented to determine, largely by process of elimination, which constituent was the transforming factor. Microbiologists endeavored during the 1930s to dispel the monomorphist tenet, prevailing as institutional dogma, largely prevailing into the 21st century.

The first Griffith Memorial Lecture indicates that Fred Griffith died on the night of 17 April 1941—though the fourth lecture indicates that he died in his apartment in February 1941 and his obituary in British Medical Journal failed to mention it.

In 1944 identification of the transforming factor was published in the Journal of Experimental Medicine by Avery, Colin MacLeod, and Maclyn McCarty of The Rockefeller Hospital. This identification departed from the prevailing belief that the protein content of chromosomes probably was the anatomical structure of genes, although it would take another decade—till Watson and Crick's 1953 paper in Nature indicating DNA's molecular structure suggesting how a molecule as seemingly simple as DNA could encode the structure of proteins—for the interpretation of DNA as genes to become widely accepted.

Biologists made little more than speculation of Griffith's report of transformation until genetics research in 1951. Griffith's report was virtually ignored by clinicians, and by the medical sector as a whole. In 1934, Griffith reported voluminous findings on the serological typing of Streptococcus pyogenes. More casually as well as medically called simply streptococcus, S pyogenes is implicated in conditions ranging from the usually minor strep throat, to the sometimes fatal scarlet fever, to the often fatal puerperal fever, to the usually fatal streptococcal sepsis. Streptococcal infection was a frequent coinfection complicating recovery from lobar pneumonia by pneumococci infection.

By 1967 pneumococcal transformation had been shown to occur in vivo naturally, and it was further shown that treatment with streptomycin during dual infection by two pneumococcal strains could increase transformation—and virulence—while for the first time pneumococcal transformation was shown to occur in the respiratory tract. In 1969 it was shown in vivo that during drug treatment of a host, pneumococci could acquire genes from antibiotic resistant streptococci, already in the host, and thereby the pneumococci could become resistant to erythromycin.