Question

Plasmid of which bacterium was first used in recombinant DNA technology
A. E. coli
B. Salmonella typhimurium
C. Haemophilus Influenzae
D. Streptococcus pneumonia

Answer 1

Plasmids are small circular pieces of DNA with their most basic level which replicate independently from the chromosomal DNA of the host. They are found mainly in bacteria, and they also happen naturally in eukaryotes and archaea, such as yeast and plants.

Complete answer:
In nature, plasmids just provide the host with one or maybe more functional advantages, including certain antibiotic resistance, deteriorating functions, and/or virulence. All the natural plasmids contain a replication origin (which governs the plasmid's genetic variability and copy number) and often have a gene that is advantageous for survival, such as with a gene for antibiotic resistance. Plasmids used in the laboratory, on the other hand, are usually artificial and engineered to insert foreign DNA into some other cell. Research lab-created plasmids minimally have a replication origin, selection marker, and cloning site. The feasibility of plasmid manipulation and the ability of plasmids to self-replicate within a cell make them promising instruments for biological sciences or technologists. A 90-kb virulence plasmid is contained in certain Salmonella typhimurium isolates. It is documented that such a plasmid is mobilizable but nonconjugative. Several names, including pSLT, MP10, pRQ28, pSTV, cryptic plasmid, and virulence plasmid, are being assigned to this plasmid.

So, the correct option is (B).

Note: Plasmids are collectively referred to as vectors or constructs "because of their artificial existence. Scientists may use one of a range of cloning methods (restriction enzyme, ligation independent) to incorporate the desired gene into a vector. Ultimately, the cloning technique is chosen depending on the plasmid you would like to clone into. The vector containing the newly inserted gene is translated into bacterial cells once cloning steps are done, and exclusively grown on antibiotic plates.