Cytoplasmic Granules in Bacteria

By Acharya Tankeshwar •  Updated: 06/17/21 •  2 min read

Concentrated deposits of certain substances which are presented/located in the cytoplasm of certain bacteria are known as cytoplasmic granules or inclusion bodies. They serve as storage areas for nutrients, e.g. volutin granules are reserves of high energy stored in the form of polymerized metaphosphate.

The number and nature of the inclusions vary depending on the bacterial species and the nutritional state of the organism’s environment. Common types of granules that are microscopically visible in certain bacteria stained with specific dyes are:

Metachromatic granules of Corynebacterium spp
Metachromatic granules of Corynebacterium spp

Cytoplasmic granules/inclusion bodies stain characteristically with certain dyes;

  1. Volutin granules appear as “metachromatic” granules, stains intense reddish-purple color with methylene blue dye (instead of blue, as one would expect), and can be observed by light microscopy.
  2. Poly-β-hydroxybutyrate (PHB) granules can be stained with lipid-soluble dyes such as Nile blue.
  3. Glycogen can be stained brown with iodine.

Metachromatic granules are characteristics of Corynebacterium diphtheriae

Acharya Tankeshwar

Hello, thank you for visiting my blog. I am Tankeshwar Acharya. Blogging is my passion. As an asst. professor, I am teaching microbiology and immunology to medical and nursing students at PAHS, Nepal. I have been working as a microbiologist at Patan hospital for more than 10 years.

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3 responses to “Bacterial Pili (Fimbriae): Types, Functions”

  1. Huda says:

    hello. I am PDH student now i wont to do my rescherch about bacteial pahogenses of fish

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