The differential medium that is used for the production of Corynebacterium diphtheria. To stimulate the growth of Corynebacterium necessary blood components or blood substitutes. To inhibit the growth of concomitant microflora to the environment is added a solution of potassium tellurite. Also, corynebacteria, growing on terricolous environments recover metallic tellurium from tellurite potassium and changes the color of the colony to black. BioWare Corynebacterium is distinguished by the form of the colonies:

• Corynebacterium diphtheriae gravis - dark grey round slightly flattened colonies with a diameter of 2 - 3 mm. Under a microscope (25x) colonies with slightly irregular edges and folded surface (a type of "Daisy").
• Corynebacterium diphtheriae mitis - dark grey round convex shiny colonies with smooth edges, with a diameter of 1.5 - 3 mm.
• Corynebacterium xerosis - dark grey round convex shiny colonies with smooth edges, a diameter of 1.2 - 2 mm.
• Corynebacterium ulcerans - dark grey round convex shiny colonies with smooth edges, a diameter of 0.5 - 1.5 mm with a silver rim.