Question

In Lederberg's replica plating experiment what shall be used to obtain streptomycin resistant strain _______________.

• A. minimal medium and streptomycin
• B. complete medium and streptomycin
• C. only minimal medium
• D. only complete medium.

Answer 1

The correct option is A minimal medium and streptomycin

The hypothesis for the experiment is that antibiotic-resistant strains of bacteria surviving an application of antibiotics had the resistance before their exposure to the antibiotics, not as a result of the exposure. If a mutation that makes a bacterium resistant to streptomycin occurs at an early stage in the growth of a colony, the resistant cell will divide and produce two, then four, then eight, and eventually a large number of resistant bacteria. Thus, if the mutation is a randomly occurring, non-adaptive process, many of the colonies that form on the non-selective plates will contain more than one antibiotic-resistant bacterium and will give rise to resistant cultures when tested for growth on selective media (minimal media).

So, the correct answer is 'Minimal media and streptomycin'.