This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General Microbiology Pa 1 (History, Microscopy, Stains and Structure and Physiology of Bacteria), Subject name: Microbiology
Swarming growth on culture is characteristic of which Gram-negative organism 
Select and explain. 
A. Clostridium welchii, B. Clostridium tetani, C. Bacillus cereus, D. Proteus mirabilis
D: Proteus mirabilis
Answer: D: Proteus mirabilis 
Explanation: 1. Swarming - Proteus has an ability to swarm (or spread) on solid media. They spread on the surface of the plate in successive waves to form a thin filmy layer in concentric circles. This is known as swarming. 2. Organism which swarm: Proteus, Clostridium tetani, V. parahemolyticus, and Serratia. Clostridium welchii - non motile Clostridium tetani - Gram positive Bacillus cereus- motile, gram positive rod Proteus mirabilis - peritrichous flagella