Index >>Bacterial Fungal Cells>>Cellular Reserve Materials

These reserve materials are deposited more or less uniformly in the cytoplasm but cannot be detected under the light microscope unless they are stained.

Generally, the cellular content of these reserve materials is small in actively growing cells and these accumulate only in carbon rich medium under limiting amounts of nitrogen.

Sometimes, these reserve materials may constitute as much as 50% of the total cellular dry weight.

These are utilized when the cells are provided with an appropriate nitrogen source and growth is resumed.

Many procaryotes accumulate volutin (metachromatic) granules which can be stained with a basic dye such as methylene blue.

These appear red when stained with a blue dye and this metachromatic nature is due to the presence of a large amount of inorganic polyphosphate.

Accumulation of these materials in bacteria occurs under conditions of starvation paricularly under sulphate starvation.

These granules rapidly disappear when the cells are provided with a sulphur source and the phosphate is then incorporated into the nucleic acids.

The volutin granules may therefore represent intracellular phosphate reserve when nucleic acid synthesis does not occur