The construction of the first recombinant DNA emerged from the possibility of linking a gene–encoding antibiotic resistance with a native plasmid (autonomously replicating circular extrachromosomal DNA) of Salmonella typhimurium. Stanley Cohen and Herbert Boyer accomplished this in 1972 by isolating the antibiotic resistance gene by cutting out a piece of DNA from a plasmid that was responsible for conferring antibiotic resistance.
The tumor-inducing (Ti) plasmid of Agrobacterium tumefaciens has been modified (disarmed) into a cloning vector that is no more pathogenic to the plants but is able to use the mechanism to deliver genes of interest into a variety of plants.
A particular type of thermostable DNA polymerase often referred to by its popular nickname ‘Taq polymerase’, a heat–resistant enzyme isolated from the bacterium Thermus aquaticus is used in PCR.
B. thuringiensis during sporulation forms intracellular crystalline bodies (cry proteins) that contain an insecticidal protein called the endotoxins.