Investigación de la transformación de Streptococcus pneumoniae en el laboratorio, y el nacimiento de la genética bacteriana y la biología molecular

Abstract

The virulence of pneumococci for mice depends on the production of a polysaccharide-capsule, which encloses the bacteria and protects it against phagocytosis. Capsulated pneumococci yield smooth, brilliant colonies designated S, but mutant strains arise frequently which have lost the capacity to sinthetise the capsule, are avirulent and rough designated R. F. Griffith discovery of bacterial “transformation” in 1928, is a landmark in the history of genetics, because hereditary determinants could be transferred from one bacteria to another, and laid the foundation for the subsequent recognition of deoxyribonucleic acid (DNA) as the hereditary material. A systematic analysis of the chemical nature of the “transforming principle”, by O. T. Avery and his colleagues during next 10 years, culminated in a formidable weight of evidence that it possessed all properties of DNA. In 1953, J. D. Watson and F. H. C Crick by a brilliant synthesis, fitted the chemical X-ray diffraction data together into a symmetrical double-helix structure, which possessed the inherent properties of genetic material, and carries the information necessary to direct all biochemical-cellular activities and self-replications. This paper describes de early rise and development of bacterial genetics and molecular biology.