The organism used in construction of the first artificial recombinant DNA by Cohen and Boyer in 1972 was :

The correct option/answer is Salmonella typhimurium.

Step-by-Step Explanation:

1. Historical Context: In 1972, Stanley Cohen and Herbert Boyer pioneered the field of recombinant DNA technology (genetic engineering) by successfully combining genetic material from two different sources.

2. The Source Organism: They isolated an antibiotic resistance gene (specifically encoding resistance to tetracycline) from a plasmid naturally occurring in the bacterium Salmonella typhimurium.

3. Construction of the Recombinant DNA: They linked this isolated gene (using restriction enzymes and DNA ligase) to a plasmid vector from Escherichia coli (E. coli).

4. Host Organism: The newly constructed chimeric/recombinant plasmid was then introduced into a host organism, which was E. coli, for replication and expression.

5. Conclusion: Therefore, the original organism used as the source to construct the first artificial recombinant DNA plasmid was the bacterium Salmonella typhimurium.