Which of the following answers about His+ prototrophs and His- auxotrophs is incorrect?

• A. His+ prototrophs are the parent bacterial cells with no mutations.
• B. His+ prototrophs require the amino acid histidine to grow.
• C. His- auxotrophs are the mutant bacterial cells which require growth factors to grow.
• D. His- auxotrophs cannot grow without the amino acid histidine.
• E. All of the above answers are correct.

Answer: (B)

Verified step by step guidance

1. Understand the definitions: His+ prototrophs are bacteria that can synthesize histidine on their own and do not require it from the environment. His- auxotrophs are mutants that cannot synthesize histidine and require it from the environment to grow.
2. Evaluate the statement: 'His+ prototrophs require the amino acid histidine to grow.' This statement contradicts the definition of His+ prototrophs, as they do not require external histidine.
3. Consider the statement: 'His- auxotrophs are the mutant bacterial cells which require growth factors to grow.' This is consistent with the definition of auxotrophs, as they need additional nutrients that prototrophs do not.
4. Analyze the statement: 'His- auxotrophs cannot grow without the amino acid histidine.' This is true because His- auxotrophs lack the ability to synthesize histidine.
5. Review the option: 'All of the above answers are correct.' Since one of the statements is incorrect, this option cannot be true.