Microorganism motile at 25deg C but not motile at 37deg C-
**Core Concept**
The question is testing the student's knowledge of the effect of temperature on the motility of microorganisms. The underlying principle is that some microorganisms exhibit temperature-dependent motility, with certain species being motile at lower temperatures but losing motility at higher temperatures.
**Why the Correct Answer is Right**
The correct answer is likely a species of bacteria that exhibits temperature-dependent motility. For example, *Proteus mirabilis* is a bacterium that is motile at room temperature (around 25°C) but loses motility at body temperature (37°C). This is due to the denaturation of its flagellin proteins at higher temperatures, which disrupts the bacterial flagella and prevents motility.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not specify a microorganism that is known to exhibit temperature-dependent motility.
* **Option B:** This option is incorrect because it does not provide a valid example of a microorganism that is motile at 25°C but not at 37°C.
* **Option C:** This option is incorrect because it does not provide a valid example of a microorganism that exhibits temperature-dependent motility.
**Clinical Pearl / High-Yield Fact**
It's worth noting that temperature-dependent motility is an important characteristic in the identification of certain bacteria, particularly those that are pathogenic. For example, *Proteus mirabilis* is a common cause of urinary tract infections, and its temperature-dependent motility can be used as a diagnostic feature.
**Correct Answer: B. Pseudomonas aeruginosa**