Mesosomes: Definition, Mechanism, Functions, Role in Cell Division and Structural Characteristics

In general, they are found in association with the nuclear area or near the site of cell division. They are absent in eukaryotes.

Lamellae are formed by flat vesicles when they are arranged in parallel. Some of the lamellae are connected to the cell membrane. The lamellar whorl can be seen in Nitrobacter, Nitro monas, and Enterococcus.

Vesicles are probably formed by invagination and tubular accretion of the plasma membrane. The structure of the gallbladder is disrupted due to constriction at equal distances.

The constriction does not cause complete separation of the tubules. Very compact spherical vesicles are seen in Chromatium and Rhodospirillum rubrum.

The vesicular bodies flatten and pile up on regular plates like thylakoids in some purple bacteria.

Salton and Owen (1976) have suggested that mesosomes are formed due to vascularization of the outer half of the lipid bilayer.

However, they are the unique components of the cell membrane, whose proteins differ from the cell membrane.


The exact structure and function of the mesosomes are not known. However, it has been suggested that these are artifacts, that is, a structure that appears in microscopic slides due to the method of preparation.

Furthermore, mesosomes are supposed to participate in respiration, but they are not analogous to mitochondria because they lack an outer membrane. Respiratory enzymes are present in the cell membrane.

In the blister of mesosomes, respiratory enzymes and electron transport components, such as ATPase, dehydrogenase, or cytochrome, are absent or present in low amounts.

This emphasizes its inability to carry out the transport process in which the membrane is energized. Furthermore, mesosomes are assumed to be a site for synthesizing some of the wall membranes.

Mesosomes could also play a role in reproduction. During binary fission, a transverse wall is formed, resulting in the formation of two cells.

Mesosomes begin the septum formation and bind the bacterial DNA to the cell membrane. Separate the bacterial DNA in each daughter cell.

In addition, the inflorescences of the mesosomes increase the area of ​​the plasma membrane, which in turn increases the absorption of nutrients.

Initial observations

They were first observed in 1953 by George B. Chapman and James Hillier, who referred to them as “peripheral bodies.” They were called “mesosomes” by JD Robertson in 1959.

The mesosome was thought to increase the cell’s surface area, assisting the cell in cellular respiration.

This is analogous to the ridges in the mitochondria in eukaryotic cells, which are finger-like projections and help eukaryotic cells undergo cellular respiration.

Mesosomes were also hypothesized to aid in photosynthesis, cell division, DNA replication, and cell compartmentalization.

How do mesosomes work?

Mesosomes are areas in the cell membrane of prokaryotic (bacterial) cells that fold inward. They play a role in cellular respiration, the process that breaks down food to release energy.

Mesosomes are part of the structure of the plasma membrane. You will find them lined up on the cell wall. They are grouped and folded to maximize their surface area.

This is important because it is necessary for cellular respiration, which is a function of the mesosomes. These folds can become distinct vesicles, which can then be used to contain material, keeping it separate from the rest of the cell.

In eukaryotes, most of this process occurs in the mitochondria. The third and final step of cellular respiration (electron transport chain) occurs in the space between the two mitochondrial membranes.

This step is critical for the cell as most of the energy from food is released during this stage.

Since prokaryotes do not contain membrane-bound organelles, they need a different approach. Instead, they use mesosomes as a site for the electron transport chain.

What are the functions of the mesosome?

Mesosomes are part of some prokaryotic cells and participate in the process of aerobic respiration.

Cellular respiration is when food is broken down, and energy is released in adenosine triphosphate molecules.

In the case of eukaryotic cells, this process takes place in an organelle known as mitochondria (also known as the cell’s house of power).

Prokaryotes do not have mitochondria and therefore have to depend on some other cellular component to carry out this process.

Mesosomes are bumps on the inner side of the cell membrane (as detected by electron microscopy) of prokaryotic cells (such as acetobacter, sporulated bacteria, etc.).

Mesosomes increase the surface area of ​​the membrane and act as the site for the electron transport chain and thus greatly assisting the process of aerobic cellular respiration.

Mesosomes and the nucleus in bacteria

Mesosomes, by consensus, are not considered inherent structures of bacterial cells.

Instead, they are artifacts of the visualization methods humans apply to these cells to prepare them for observation by electron microscopy.

The word “mesosome” doesn’t even appear in my college-level biology textbooks written after 2005.

Also, bacteria don’t have a nucleus, at least not in the traditional way that term is described, so there is nothing for mesosomes to stick together.

Recent research suggests that mesosomes may be involved in responses to cell injury or hydrogen peroxide synthesis.

But research in this area is sparse and acknowledges the lack of competitive research linking mesosomes to their traditionally attributed properties, such as participation in respiration and cell division.

What is the role of mesosomes in cell division?

Mesosomes are cellular organelles and are typically present in prokaryotes. They are analogous to mitochondria in eukaryotes. Mesosomes are part of the cell membrane structure located on the inner side.

Some of the critical functions of mesosomes include increasing the surface area of ​​the plasma membrane and assisting in electron transport, photosynthesis, cell wall formation, and the like.

Mesosomes help with cell division, assisting in cell wall synthesis and DNA replication. Another function they serve is the uniform distribution of chromosomes in the daughter cells of the parent cell.

During cell division, a transverse wall is formed. Mesosomes begin forming this transverse wall, or septum, and bind bacterial DNA to the cell membrane. This results in separating the bacterial DNA in each of the resulting daughter cells.

Between the two types of mesosomes (septal and lateral), septal mesosomes participate in forming the transverse wall. The bacterial chromosome is also attached to the septal mesosomes.

Structural characteristics of Bacillus subtilis mesosomes (chondroid) after freezing

The frozen cells of Bacillus subtilis have been studied with the electron microscope.

The outer surface of the plasma membrane, the side facing the cell wall, is covered with numerous granules and short strands, each of which is approximately 50 A in diameter.

These strands are occasionally seen to enter the cell wall. The inner surface of the plasma membrane, that is, the side facing the cytoplasm, appears to be dotted with small particles measuring approximately 50 A.

The envelope of mesosomes differs from the plasma membrane. Blunt bumps emerge from its outer surface; the inner surface appears smooth.

As described by other investigators, after negative staining with phosphor-phosphatic acid, Stalked particles were not observed on any membrane surface in our material.

Prefixed specimen preparations were also made in osmium tetroxide before freeze etching. Under these conditions, the bacterial membranes appeared to be surprisingly well preserved.

In contrast to unfixed, directly frozen cells, some osmium tetroxide-fixed preparations showed differentiation into the cytoplasm and nucleoplasm, which allowed us to observe the close association of the mesosome with the latter.