Question

Which of the following substances was used as a screening agent in replica plating experiment?

• A. Vitamin B${}_{12}$
• B. Cofactors and streptomycin
• C. Amino acid lysine
• D. Antibiotic streptomycin

Answer 1

The correct option is D Antibiotic streptomycin

Replica plating technique rapidly transfers microorganism colonies to numerous petri plates and is used for detection of auxotrophs. It was given by Joshua Lederberg & Esther Lederberg. A pattern of colonies growing on the complete medium is imprinted on velveteen by inverting the petri plate. Plates with streptomycin were pressed on that master plate to transfer the impression. Cells carrying streptomycin resistance grow on the plate with streptomycin. The areas on the second plates where colonies fail to grow to correspond to wild-type colonies without streptomycin resistance on the original plate which is then used for isolation and multiplication of mutant colonies. The correct answer is D.