This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Spirochetes, Subject name: Microbiology
[{'content': 'Which of the following organisms is visualized by gram staining: \nSelect and explain. \nA. Treponema, B. Borrelia, C. Mycoplasma, D. Mycobacterium', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans: b (Borrelia)Ref: Ananthanarayan and Paniker's Textbook of Microbiology, 8th ed.* Treponema - do not stain by ordinary method. Prolonged Giemsa, Fontana or Levaditis method is used* Mycoplasma - has no cell wall. So they are gram negative but are better stained by Giemsa* Mycobacterium-resist decolonisation by alcohol even without mordant effect of iodine. Can be called gram positive even though it is not used for diagnosis* Borrelia - readily stain by ordinary methods and are gram negative", 'role': 'assistant'}]