This document discusses different types of cell inclusions found in prokaryotic cells, which are reserve deposits that accumulate nutrients when plentiful and use them when the environment is deficient. The main types discussed are metachromatic granules, which contain inorganic phosphate; polysaccharide granules containing glycogen and starch; lipid inclusions containing polymers like PHB; sulfur granules in sulfur-oxidizing bacteria; and carboxysomes containing the enzyme RuBisCO for carbon fixation in photosynthetic bacteria. Cell inclusions can be identified through staining and serve important metabolic functions for nutrient storage.

1. CELL INCLUSIONS
Dr. P. Saranraj

2. CELL INCLUSIONS
Within the cytoplasm of prokaryotic cells,
several kinds of reserve deposits, known as
Inclusions or Cell Inclusions.
Cells may accumulate certain nutrients when
they are plentiful and use them when the
environment is deficient.
Some inclusions arc common to a wide
variety of bacteria, whereas others are
limited to a small number of species and
therefore serve as a basis for identification.

3. TYPES OF CELL INCLUSIONS
1) Metachromatic Granules
2) Polysaccharide Granules
3) Lipid Inclusions
4) Sulfur Granules
5) Carboxysomes

4. METACHROMATIC GRANULES
Metachromatic granules are large inclusions
that take their name from the fact that they
sometimes stain red with certain blue dyes
such as Methylene blue.
They are collectively called as Volutins.
Volutin represents a reserve of inorganic
phosphate (polyphosphate) that can be used in
the synthesis of ATP. It is generally formed by
cells that grow in phosphate - rich
environments.
It is present in Bacteria (Corynebacterium
diptheriae – Causative agent of “Dipteria”),

5. POLYSACCHARIDE GRANULES
Polysaccharide granules typically consist of
Glycogen and Starch.
In the presence of Iodine, Glycogen granules
appears in Red and Starch granules appears
in Blue.

6. LIPID INCLUSIONS
Lipid inclusions appear in various species of
Mycobacterium, Bacillus, Azotobacter,
Spirillum and other genera.
A common lipid-storage material, one unique
to bacteria, is the polymer PHB (Poly – β –
hydrobybutyric acid).
Lipid inclusions are revealed by staining cells
with fat-soluble dyes, such as Sudan dyes.

7. SULFUR GRANULES
Certain bacteria - for example, the
"Sulfur bacteria" that belong to the
genus Tliiobacillils sp. derive energy by
oxidizing sulfur and sulfur -containing
compounds.
These bacteria may deposit sulfur
granules in the cell, where they serve as
an energy reserve.

8. CARBOXYSOMES
Carboxysomes are inclusions that contain the
enzyme Ribulose 1, 5 - diphosphate
carboxylase.
Photosynthetic bacteria use carbon-di-oxide
as their sole source of carbon and require
the Ribulose 1, 5 - diphosphate carboxylase
for Carbon-di-oxide fixation.
Carboxysomes containing bacteria are
Nitrifying bacteria, Cyanobacteria and
Thiobacilli.