Question

Tumbling motility is typical for ________.

• A. Listeria monocytogenes
• B. Mycobacterium tuberculosis
• C. Escherichia coli
• D. Campylobacter jejuni

Hint:

Remember the temperature-dependent motility of Listeria:
- At $20^\circ\text{C}$ to $25^\circ\text{C}$ = Motile (distinctive "tumbling" motion under wet mount microscopy).
- At $37^\circ\text{C}$ = Non-motile.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Bacterial motility patterns are key diagnostic characteristics used to identify pathogens.
These patterns depend on flagellar structure, arrangement, and environmental temperature.
Detailed Explanation:
Listeria monocytogenes is a Gram-positive, non-spore-forming, facultatively anaerobic rod-shaped bacterium that causes listeriosis, a serious foodborne infection.
This organism exhibits a characteristic end-over-end "tumbling motility" when grown at room temperature ($20^\circ\text{C}$ to $25^\circ\text{C}$).
At these lower temperatures, the bacterium synthesizes up to four flagella in a peritrichous arrangement, enabling this tumbling movement.
At $37^\circ\text{C}$ (human body temperature), the expression of flagellar proteins is down-regulated, and the organism becomes non-motile, relying instead on host cell actin polymerization for movement inside cells.
Let us review the motility patterns of the other options:
- Mycobacterium tuberculosis is strictly non-motile and lacks flagella.
- Escherichia coli exhibits a swimming or running motility mediated by peritrichous flagella.
- Campylobacter jejuni has a single polar flagellum at one or both ends, producing a rapid, darting, or corkscrew-like motility.

Step 2: Final Answer:
Tumbling motility is a characteristic diagnostic feature of Listeria monocytogenes.