Escherichia coli was the first genetically engineered organism in the landmark 1973 experiment by Herbert Boyer and Stanley Cohen.
Boyer and Cohen inserted recombinant DNA into E. coli, demonstrating that a DNA molecule assembled from different sources could be introduced into a bacterial cell and maintained there. Their work helped establish recombinant-DNA technology and became a foundation of modern biotechnology.
E. coli was a practical model because it grows quickly, is well studied, and can carry engineered plasmids. Plasmids are small, usually circular DNA molecules that replicate separately from the bacterial chromosome. Researchers can place selected genes into plasmids and use marker genes to identify cells that received them. The 1973 experiment did not create the first organism with any naturally occurring mutation; it demonstrated deliberate laboratory transfer and propagation of recombinant DNA. Today, engineered E. coli produces research proteins, industrial enzymes, and some medicines, although production strains are carefully selected and controlled.