Cohen and Boyer created the first recombinant DNA using plasmid of :

The correct answer is Option (3) → Salmonella typhimurium

Option (1) Escherichia coli — Incorrect. E. coli is the usual host and source of cloning vectors such as pBR322, but the first recombinant DNA used another bacterium’s plasmid.

Option (2) Thermus aquaticus — Incorrect. This bacterium of hot springs gives Taq polymerase, the heat-stable enzyme used in PCR.

Option (3) Salmonella typhimurium — Correct. In 1972 Stanley Cohen and Herbert Boyer linked an antibiotic resistance gene with a native plasmid of this bacterium, making the first recombinant DNA.

Option (4) Bacillus thuringiensis — Incorrect. This bacterium is the source of the Bt toxin (cry) genes used in pest-resistant crops.

NCERT Extract:
Principles of Biotechnology – “… Let us now focus on the first instance of the construction of an artificial recombinant DNA molecule. 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 extra-chromosomal 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 which was responsible for conferring antibiotic resistance.”