Inclusion Bodies

Reserve material in prokaryotic cells is stored in the cytoplasm in the form of inclusion bodies. These are not membrane-bound systems and lie free in the cytoplasm, e.g., phosphate granules, cyanophycean granules, and glycogen granules. Gas vacuoles are found in blue-green and purple and green photosynthetic bacteria. Cell inclusions also called ergastic bodies are non-living substances present in the cells which may be present in soluble or insoluble states and can be organic or inorganic in nature. They belong to three categories – reserve food, excretory or secretory products, and mineral matter. Inclusion bodies are unusual structures with different sizes and shapes and are normally observed in nerve, epithelial, or endothelial cells.

Inclusion bodies can be seen in both prokaryotic and eukaryotic cells. They are a wide variety of inclusion bodies in distinct kinds of cells. In prokaryotes, they are mainly formed to store reserve materials. In animal cells, they store fats and sugars that are ready for cellular respiration, and in plant cells, they store granules of materials like glycogen, starch, etc.

General Features of Inclusion Bodies

• They act as reserve deposits.
• Cell inclusions are generally acidophilic.
• A large number of nutrients can be stored in them by the cells and utilized when there is a shortage in the environment.
• These can be seen as pink structures under the microscope when stained with gypsum or methylene blue dye.

Classification of Inclusion Bodies

Inclusion bodies can be classified into distinct types based on their location, either at the nucleus or cytoplasm or at both the cell organelles. The different types of inclusion bodies are as follows:

• Intranuclear inclusions
• Infection inclusion bodies.
• Intracytoplasmic inclusions.
• Physiological inclusion of bodies.

Inclusion bodies can exist in a bacterium or eukaryotic cell in the form of cystic lesions, fungal infections, virus-infected cells, bacterial infections, autoimmune diseases, neoplasms, and blood dyscrasias.

Viral Inclusion Bodies

Some of examples of viral inclusion bodies are:

Intracytoplasmic Eosinophilic

• Negri bodies in rabies
• Paschen bodies in variola
• Bollinger bodies in fowlpox
• Handerson-Patterson bodies in Molluscum Contagiosum
• Eosinophilic inclusion bodies in boid inclusion body disease

Intranuclear Eosinophilic

• Torres bodies in yellow fever
• Cowdry type A in Herpes simplex virus
• Cowdry type B in Polio and adenovirus

Intranuclear Basophilic

• Cowdry type B in adenovirus
• Owl’s eye appearance in cytomegalovirus

Key Points on Inclusion Bodies

• Inclusion bodies are the bacteria using hydrogen sulfide as an electron source containing sulfur granules.
• These are cytoplasmic or nuclear combinations of stainable substances.
• A few bacteria keep in reserve excess carbon in the form of glycogen or polyhydroxyalkanoates.
• When the genes from one organism are expressed in some other organism, the protein is synthesized from inclusion bodies.

The cell is the structural and functional unit of life. The prokaryotic cells constitute bacteria, blue-green algae, mycoplasma, and PPLO( Pleuro Pneumonia Like Organisms). The size of prokaryotic cells is usually small ( 0.1- 5.0 μm ). It has one envelope organization. In prokaryotes, DNA is naked, that is, without an association with histones and it is usually circular. The size of the eukaryotic cells is larger than the prokaryotic cell ( 5-100 μm ). It has two envelope organization. In these cells, nuclear DNA is associated with histone proteins. Nuclear DNA is linear while extranuclear DNA is commonly circular. The cytoplasm is jelly-like semi-fluid bulk of protoplasm excluding the nucleus. It includes all other components – cytoplasmic matrix, cell organelles, and cell inclusions. Cell organelles are sub-cellular structures. They can carry out their functions even outside the cytoplasm provided they are supplied with substances, which are normally provided by the cell. Cell organelles include Mitochondira, Plastids, Endoplasmic Reticulum (ER), Golgi Complex, Lysosomes, Microbodies, Ribosomes, Cytoskeletal Structures, Flagella and Cilia, Centrioles, Vacuoles and Nucleus. Hereunder is a detailed explanation of Ribosomes and inclusion bodies.