Tabon Gram wata dabara ce ta dakin gwaje-gwaje da ake amfani da ita don bambance nau'in kwayoyin cuta da karkasa su zuwa manyan nau'i biyu, bisa tsarin bangon tantanin su. Wannan dabarar ta ƙunshi lalata ƙwayoyin ƙwayoyin cuta tare da rini na kristal, sannan iodine, barasa, da safranin, waɗanda ke ɓata sel daban-daban dangane da kaurin bangon tantanin su. Kwayoyin da ke riƙe da tabon crystal violet kuma suna bayyana purple a ƙarƙashin na'urar hangen nesa ana kiran su "Gram-positive," yayin da waɗanda ba su riƙe tabon ba kuma suna bayyana ja ana kiran su "Gram-negative." Dabarar tabon Gram ana kiranta da sunan wanda ya ƙirƙira ta, masanin ƙwayoyin cuta ɗan Danish Hans Christian Gram.