All are motile except?
**Core Concept**
The question tests the student's knowledge of the motility of different types of bacteria. In microbiology, motility is the ability of bacteria to move using various mechanisms, such as flagella, pili, or gliding. Understanding the motility of different bacteria is crucial in identifying and characterizing them.
**Why the Correct Answer is Right**
The correct answer is likely a type of bacteria that is non-motile, meaning it lacks the ability to move. This could be due to various reasons, such as the absence of flagella or other motility structures. For example, some bacteria like *Staphylococcus aureus* are non-motile due to the absence of flagella. On the other hand, bacteria like *Escherichia coli* are motile due to the presence of flagella.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because *Pseudomonas aeruginosa* is a highly motile bacterium that uses its single polar flagellum to move.
* **Option B:** This option is incorrect because *Klebsiella pneumoniae* is also motile, using its peritrichous flagella to move.
* **Option C:** This option is incorrect because *Proteus mirabilis* is a highly motile bacterium that uses its peritrichous flagella to move.
**Clinical Pearl / High-Yield Fact**
It's essential to note that the ability of bacteria to move can affect their virulence, colonization, and infection dynamics. Motile bacteria can easily colonize new sites and evade the host's immune system.
**Correct Answer:** D.