<prompt> Which of the following organisms is visualized by gram staining:TreponemaBorreliaMycoplasmaMycobacterium  <response>: Ans: b BorreliaRef: Ananthanarayan and Panikers 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 