What are metachromatic granules? Name the bacterium of which they form a characteristic feature.
The metachromatic granules are collectively known as volutin that represents a reserve of inorganic phosphate (polyphosphate) that can be used in the synthesis of ATP. These large granules have been named so because they sometimes stain red with certain blue dyes like methylene blue. The metachromatic – granules are a characteristic feature of Corynebacterium diphtheriae, the causative agent of diphtheria.