Question

Amey adds plasmid to the bacteria cells and then inoculate it to the plates containing nutrient media. Select the correct statement regarding cell and plasmid.

• A. Plasmid should contain an auxotrophic mutation, and the medium should contain the missing nutrient.
• B. Plasmid should contain a gene for producing a nutrient, and the bacterial chromosome should contain an auxotrophic mutation.
• C. Bacterial chromosome should contain an antibiotic resistance gene, and the medium should contain the antibiotic.
• D. Plasmid should contain a gene for producing an antibiotic, and the bacterial chromosome should contain a gene for antibiotic resistance.
• E. Bacterial chromosome should contain an auxotrophic mutation, and the medium should contain the missing nutrient.

Answer 1

The correct option is B Plasmid should contain a gene for producing a nutrient, and the bacterial chromosome should contain an auxotrophic mutation.

Replica plating is a technique to rapidly transfer microorganism colonies too numerous petri plates and is used for detection of auxotrophs. Auxotrophs are the bacteria that are incapable of utilizing/synthesizing certain compounds and can grow on minimal media plus the specific growth supplement for which they are mutant. Plasmid must contain the gene for synthesis of that nutrient and a selectable marker gene (antibiotic resistance gene) to allow detection of transformed bacterial colonies on minimal media containing the antibiotic. The correct answer is B.