Question

selective agents
two agar plates, one containing the antibiotic streptomycin and one without antibiotics, are inoculated with e. coli. after incubation, the streptomycin - negative plate has many bacterial colonies, while the streptomycin - positive plate has only a few colonies. samples of the colonies from the positive plate are placed on another positive plate, and after incubation many colonies grow. in this experiment, what is the selective agent?
multiple choice
the period of incubation
the agar medium
the e. coli
the antibiotic streptomycin

Explanation:

A selective agent is something that influences the survival and growth of organisms. In this experiment, streptomycin allows only resistant E. coli to grow on the plate with it, while non - resistant ones are inhibited. The incubation period, agar medium, and E. coli itself are not selective agents in this context. It is the antibiotic streptomycin that selectively allows the growth of resistant bacterial colonies.

Answer:

D. the antibiotic streptomycin