Step 1: Understanding the Concept:
Bacterial flagellation represents a primary morphological character used in taxonomic classification and identification.
Based on the arrangement and number of flagella on the cell surface, bacteria are categorized as monotrichous, lophotrichous, amphitrichous, or peritrichous.
Step 2: Detailed Explanation:
Let us analyze the flagellar arrangements of the listed bacterial species:
1. Pseudomonas aeruginosa (C): This is a classic Gram-negative, rod-shaped, non-spore-forming bacterium. It exhibits a monotrichous flagellar arrangement, meaning it possesses a single polar flagellum located at one end of the cell. This polar flagellum provides rapid, directional swimming motility. Thus, (C) is correct.
2. Escherichia coli (A): Exhibits a peritrichous flagellar arrangement, where multiple flagella are distributed uniformly across the entire cell surface.
3. Salmonella typhi (B): Also possesses a highly motile peritrichous flagellar system that coordinates tumbling and running motility.
4. Bacillus subtilis (D): A Gram-positive soil bacterium that is also peritrichously flagellated during its vegetative state.
Thus, only Pseudomonas aeruginosa represents an organism with a single polar flagellum.
Step 3: Final Answer:
Therefore, the correct organism is Pseudomonas aeruginosa.