Mycoplasmosis and ureaplasmosis
Mycoplasmas – the smallest free-living microorganisms (prokaryotes), belong to the family of Musplasmataceae, which is part of the Mycoplasmatales class of the Mollicutes class. Mycoplasmas are extremely polymorphic microorganisms. In smears prepared from organs and cultures, round, ring-shaped, oval, cocciform and filiform formations are found. Cells have a different size, which according to various authors, ranges from 125 to 600 nm. The features of mycoplasmas that are unique to prokaryotes are: the absence of the cell wall and its precursors (which biophysically brings them closer to the L-forms of bacteria). Instead of the cell wall, they have a three-layer membrane, a cytoplasm with a nuclear substance, granules and vacuoles. The membrane consists of polar lipids and proteins. The average cell sizes of mycoplasmas are 0.3–0.8 μm, and the average diameter is 0.42 μm. However, there are species that form, at certain stages of development, extended whisker cells up to 150 microns in length. Mycoplasmas have a minimal number of organelles; smallest genome size among prokaryotes (500-1000 MDa), low (23-40%) content of G + C in DNA. Typically, mycolasm colonies are parasitic on eukaryotic cell membranes, using the contents of the cells as food. The main component of parasitic species is free and esterified cholesterol, which provides energy and structural organization of the cell.
The chemical composition of the cell consists of protein in the amount of 59.80%, total nitrogen – 11.20%, nucleic acids – 6.63%, lipids – 5.10%, and fatty acids – 2.35%. The amount of protein in the dry mass of mycoplasmas ranges from 54 to 62 mg, it includes up to 17 amino acids. In addition, the protein component includes various enzymes that play a major role in the metabolism of microbial cells.
The genome of a mycoplasma cell consists of a circular two helical DNA. In this case, genome replication occurs, as a rule, at one growth point. It is believed that the shape of the cell depends on the development cycle of the microorganism.
Mycoplasmas, due to their structural features, poorly adapt on nutrient media. Some strains cause turbidity, while others form a light film. Some strains grow in the upper layer of the nutrient medium, others in the bottom part. On semi-liquid media with growth additives, mycoplasmas grow at an injection or form suspended tiny colonies.
On dense nutrient media, mycoplasmas form characteristic colonies resembling fried eggs. Moreover, in primary crops, growth begins on the 3rd and 7th day, adapted strains grow much faster. In the case of prolonged cultivation of mycoplasma deep in the agar medium, precipitation bands form, which are the result of enzymatic activity. The colonies germinate deeply, the size of the colonies does not exceed 2 mm. Colonies of mycoplasmas isolated from pathological material and belonging to different species are morphologically similar. It was noted that an increase in the incubation period increases the frequency of pathogen release. Therefore, crops on nutrient media are recommended to withstand up to 10 days.
Mycoplasma growth is determined by the presence of various nutrients. Of the protein substances, albumin, sterols, carbohydrates and vitamins are needed for their growth. The need for mycoplasmas in phospholipids, salts of bile and fatty acids was also noted. Mycoplasmas propagate by equal and unequal division of the mother cell, budding, fragmentation, as well as by the formation of “elementary bodies” in the cytoplasm or on the limiting membrane of the cell, size 0.100-0.250 microns.
In the process of studying metabolism, the biochemical activity of mycoplasmas was established. Based on this trait, mycoplasmas are divided into enzymatically active and enzymatically inactive.
Mycoplasmas are very common in nature. Most of them are parasites of plants and animals, however, some species are saprophytes. In total, there are over a hundred species of mycoplasmas and over two hundred of their subspecies (serovars).
Man is a natural reservoir for at least 17 species of mycoplasmas. As already noted, most mycoplasmas, like chlamydia, rickettsia, bartonella and viruses, are cellular parasites. But, unlike the mentioned microorganisms, they prefer to inhabit not the nucleus or cytoplasm, but cell membranes, located on their surfaces, deepening into them, or even “merging” with them. In the human body, the objects of parasitism for mycoplasmas are epithelial cells, nerve fibers, parenchymal organs, muscles, joints, glands, as well as blood cells and other microorganisms that normally or pathologically inhabit human organs. Pathogens for humans are considered M. pneumoniae (causes respiratory mycoplasmosis), M.arthritidis (associated with joint diseases – arthritis) and a group of genital mycoplasmas M. hominis, M. genitalium, M.fermentans and U.urealyticum that cause damage to the genitourinary organs.