This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bacteriology, Subject name: Microbiology
[{'content': 'The "string of pearl" colonies on nutrient agar is produced by \nSelect and explain. \nA. Klebsiella, B. Proteus, C. Bacillus anthracis, D. Salmonella', 'role': 'user'}, {'content': "Answer: C \nExplanation: When Bacillus anthracis is grown on the surface of a solid medium containing 0.05-0.5 units of Penicillin/ml, in 3-6hours the cells grow large, spherical and in chains on the surface of the agar resembling a string of pearls. This string of pearls reaction clearly differentiates bacillus anthracis from Bacillus cereus and other aerobic bearers. Reference: Textbook of Microbiology; Anathanarayan and panicker's; 10th edition; Page no: 252", 'role': 'assistant'}]