Question

Gram negative curved spiral rods which are motile by means of single polar flagellum belong to the genus _______

• A. Brucella
• B. Listeria
• C. Salmonella
• D. Campylobacter

Hint:

Remember these key morphological identifiers:
- Campylobacter = Curved/gull-wing shape, Gram-negative, single polar flagellum, corkscrew motility.
- Listeria = Gram-positive rod, tumbling motility.
- Salmonella = Gram-negative straight rod, peritrichous flagella.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Bacterial identification relies heavily on morphological characteristics, Gram-staining reaction, arrangement, and motility patterns.
Various foodborne pathogens exhibit distinct morphological features that allow them to be classified into specific genera.

Step 2: Detailed Explanation:
Let us analyze the morphological and physiological features of the genera listed in the options:
-Campylobacter:
This genus consists of Gram-negative, slender, spirally curved or comma-shaped rods.
They often appear in pairs resembling "s-shapes" or "gull-wing" profiles.
They are highly motile, exhibiting a characteristic rapid, darting, corkscrew-like movement.
This motility is mediated by a single polar flagellum (monotrichous flagellation) located at one or both ends of the cell.
They are microaerophilic pathogens, and species like Campylobacter jejuni are major causes of foodborne gastroenteritis associated with raw milk consumption.
Let us compare this with the other options:
- Brucella: Gram-negative, very small coccobacilli that are non-motile and lack flagella.
- Listeria: Gram-positive, small coccobacilli or short rods that exhibit a characteristic tumbling motility at room temperature via peritrichous flagella.
- Salmonella: Gram-negative, straight bacilli that are motile via peritrichous flagella, not a single polar flagellum.

Step 3: Final Answer:
Gram-negative, curved spiral rods that are motile via a single polar flagellum belong to the genus Campylobacter.