Which of the following best describes what happens when a strain of bacteria possesses a temperature-sensitive mutation?

• A. The bacteria can survive only in the absence of oxygen.
• B. The bacteria lose their cell wall at high temperatures.
• C. The bacteria are resistant to all antibiotics at any temperature.
• D. The bacteria exhibit normal growth at permissive temperatures but show defective growth or function at non-permissive temperatures.

Answer: (D)

Verified step by step guidance

1. Understand the concept of a temperature-sensitive mutation: it is a genetic mutation that causes a protein or cellular function to work normally at a certain (permissive) temperature but to malfunction or become inactive at a different (non-permissive) temperature.
2. Recognize that such mutations do not generally affect traits like oxygen requirement or antibiotic resistance directly; instead, they affect the stability or function of proteins depending on temperature.
3. Analyze the options given and identify that the key feature of temperature-sensitive mutations is the conditional phenotype—normal function at one temperature and defective function at another.
4. Recall that this type of mutation is often used in microbiology to study essential genes by shifting temperatures to observe effects on bacterial growth or function.
5. Conclude that the best description is that bacteria with temperature-sensitive mutations grow normally at permissive temperatures but show defective growth or function at non-permissive temperatures.