Mycoplasma: Size and Its Cell Wall

Mycoplasma is naturally resistant to antibiotics that interfere with cell wall formation (like the beta-lactam antibiotics). 

They can either be parasitic or saprotrophic in nature. 

Several species, including M. pneumoniae, which is a significant cause of “walking” pneumonia and other respiratory disorders, and M. genitalium, which is suspected of being involved in pelvic inflammatory diseases, are pathogenic in humans. 

Mycoplasma species are the smallest bacteria cells that have been discovered to date. 

They can survive in the absence of oxygen and come in a variety of shapes. 

For example, M. genitalium is flask-shaped (approximately 300 x 600 nm), whereas M. pneumoniae is more elongated (approximately 300 x 800 nm) (about 100 x 1000 nm).

Animals are infected by hundreds of different mycoplasma species.

Originally coined by Albert Bernhard Frank in 1889 to describe an altered state of plant cell cytoplasm as a result of infiltration by fungus-like microorganisms, the term mycoplasma is derived from the Greek words mykes (fungus) and plasma (formed).

The genus name Mycoplasma was later proposed by Julian Nowak for a group of filamentous microorganisms that were thought to have both cellular and acellular stages in their life cycles, which could explain why they were visible under a microscope but passed through filters impermeable to other bacteria.

Later, the name pleuropneumonia-like organisms (PPLO) was given to Mycoplasma, which refers to organisms that are similar in colonial morphology and filterability to the causative agent (a mycoplasma) of contagious bovine pleuropneumonia in terms of filterability.

Structure

The genus Mycoplasma contains more than 100 species, all of which are pathogenic.

In the class Mollicutes, which includes Mycoplasma, microbes are found that are either parasites or commensals of humans, animals, and plants. 

Mycoplasma is a genus that has hosts that are both vertebrates and arthropods. 

In the bacteria Mycoplasma and Phytoplasma, it has been demonstrated that dietary nitrogen availability affects codon bias and genome evolution.

Mycoplasmas are a type of bacterium that belongs to the Mollicutes family. 

In terms of size, they are among the smallest free-living organisms on the planet (diameters ranging from 0.2 to 0.3 microns).

The presence of mycoplasmas in the pleural cavities of cattle suffering from pleuropneumonia has been discovered. These organisms are referred to as MLOs (mycoplasma-like organisms) or PPLOs (plasma-like organisms) (pleuropneumonia-like organisms).

The morphology of cells and colonies

• There is no cell wall present, and the plasma membrane serves as the cell’s outer boundary.

• Because they lack cell walls, these organisms have the ability to change their shape and are known as pleomorphic.

• The absence of a nucleus and other organelles that are attached to membranes.

• Genetic material consists of a single DNA duplex that is completely naked.

• The ribosomes are of the 70S type.

• Contain a replicating disc at one end, which aids in the replication process as well as the separation of genetic materials from one another.

• Despite the fact that some are saprophytes, the vast majority are parasites of both plants and animals.

•  The parasitic nature of mycoplasmal bacteria is due to their inability to synthesise the growth factor required for reproduction.

Mycoplasma bacteria have a number of distinctive characteristics

Due to the absence of a rigid cell wall, Mycoplasma can contort into a wide variety of shapes, ranging from round to oblong in appearance.

As a result, they do not fit into the categories of rods, cocci, or spirochetes.

Mycoplasmas are some of the tiniest of all the bacteria on the planet.

From a spherical or pear shape (0.3 to 0.8 micrometres [0.0000117 to 0.0000312 inch] in diameter) to that of a slender branched filament (0.0000117 to 0.0000312 inch), the cell can take on a variety of shapes (up to 150 micrometres [0.00585 inch]).

Mycoplasma species are mostly facultatively anaerobic, colonial microorganisms that do not have cell walls, which makes them particularly dangerous. 

In ruminants, carnivores, mice, and humans, Mycoplasma species are parasites of the joints and mucous membranes lining the respiratory, genital, and digestive tracts, as well as the respiratory, genital, and digestive tracts of humans.

The accumulation of toxic byproducts excreted by the bacterium in the host’s tissues results in tissue damage. 

pneumoniae is a bacteria that causes pneumonia in humans, which is common but rarely fatal.

A Mycoplasma infection can also cause a severe immune response in the host, which can be fatal.

Mycoplasmas are spherical to filamentous cells that have no cell walls and are found in the environment.

The attachment organelle of filamentous M pneumoniae, M genitalium, and several other pathogenic mycoplasmas can be found at the tip of their filaments. 

On agar, colonies in the shape of fried eggs can be observed. 

The mycoplasmas are thought to have evolved from Gram-positive bacteria through degenerative evolution, and they are phylogenetically most closely related to some clostridial species. 

As the smallest self-replicating organisms with the smallest genomes (a total of approximately 500 to 1000 genes), mycoplasmas are low in the nucleotides guanine and cytosine and high in guanine. 

Mycoplasmas require a high level of nutritional precision. 

Many prokaryotes require cholesterol, which is a characteristic that distinguishes them from other organisms.

Ureaplasmas require urea in order to grow, which is another unusual characteristic.

Antigens on the surface of mycoplasmas include membrane proteins, lipoproteins, glycolipids, and lipoglycans, among other things.

Some membrane proteins are subjected to spontaneous antigenic variation, while others are not. Inhibition of growth is caused by antibodies to surface antigens. 

A variety of serological tests have been developed and are useful in the classification of microorganisms.

In terms of size and complexity, mycoplasmas are the smallest and most basic of all self-replicating bacteria.

Among the organelles required for growth and replication in the mycoplasma cell are a plasma membrane, ribosomes, and a genome composed of a circular double-stranded DNA molecule.

They are classified as Mollicutes, as opposed to all other prokaryotes because they lack cell walls, which distinguishes them from the rest of the prokaryotes (mollis, soft; cutis, skin). 

The innocuous term mollicutes is frequently used as a catch-all term to describe any member of the class, effectively replacing the older term mycoplasmas in this context.

Conclusion

Mycoplasma is a genus of bacteria that does not have a cell wall that protects the cell membranes from infection. 

They are the most basic self-replicating bacteria known to science.

 Coccus is the most basic form of the bacterium Mycoplasma. 

Mollicutes are another name for this group of organisms.