Four subspecies are recognized: C. d. mitis, C. d. intermedius, C. d. gravis, and C. d. belfanti. The four subspecies differ slightly in their colonial morphology and biochemical properties, such as the ability to metabolize certain nutrients, but all may be toxigenic (and therefore cause<unk>  or not toxigenic.<unk>  produces<unk> toxin which alters protein function in the host by inactivating the elongation factor EF-2. This causes pharyngitis and 'pseudomembrane' in the throat. The<unk> toxin gene is encoded by a bacteriophage found in toxigenic strains, integrated into the bacterial chromosome. To accurately identify<unk> , a Gram stain is performed to show Gram-positive, highly pleomorphic organisms with no particular arrangement. Special stains like Albert's stain and Ponder's stain are used to demonstrate the metachromatic granules formed in the polar regions. The granules are called polar granules, Babes Ernst granules, volutin granules etc. An enrichment medium, such as Löffler's medium, is used to preferentially grow<unk> . After that, a differential plate known as tellurite agar, allows all Corynebacteria (including<unk>  to reduce tellurite to metallic tellurium. The tellurite reduction is colorimetrically indicated by brown colonies for most Cornyebacterium species or by a black halo around the<unk>  colonies. A low concentration of iron is required in the medium for toxin production. At high iron concentrations, iron molecules bind to an aporepressor on the beta bacteriophage, which carries the Tox gene. When bound to iron, the aporepressor shuts down toxin production. Elek's test for toxigenicity is used to determine whether the organism is able to produce the<unk> toxin.
Corynebacterium diphtheriae
Bacillus anthracis
Streptococcus bovis
Staphylococcus aureus
Corynebacterium pseudotuberculosis
Streptococcus pyogenes
Rhodococcus equi
Corynebacterium striatum