Mycoplasma is a genus of bacteria that, like the other members of the class Mollicutes, lack a cell wall, and its peptidoglycan, around their cell membrane. The absence of peptidoglycan makes them naturally resistant to antibiotics such as the beta-lactam antibiotics that target cell wall synthesis. They can be parasitic or saprotrophic. Several species are pathogenic in humans, including M. pneumoniae, which is an important cause of "walking" pneumonia and other respiratory disorders, and M. genitalium, which is believed to be involved in pelvic inflammatory diseases. Mycoplasma species are among the smallest organisms yet discovered, can survive without oxygen, and come in various shapes. For example, M. genitalium is flask-shaped, while M. pneumoniae is more elongated, many Mycoplasma species are coccoid. Hundreds of Mycoplasma species infect animals.
Phytoplasmas are obligate intracellular parasites of plant phloem tissue and of the insect vectors that are involved in their plant-to-plant transmission. Phytoplasmas were discovered in 1967 by Japanese scientists who termed them mycoplasma-like organisms. Since their discovery, phytoplasmas have resisted all attempts at in vitro culture in any cell-free medium; routine cultivation in an artificial medium thus remains a major challenge. Phytoplasmas are characterized by the lack of a cell wall, a pleiomorphic or filamentous shape, a diameter normally less than 1 μm, and a very small genome.
Mollicutes is a class of bacteria distinguished by the absence of a cell wall. The word "Mollicutes" is derived from the Latin mollis, and cutis. Individuals are very small, typically only 0.2–0.3 μm in size and have a very small genome size. They vary in form, although most have sterols that make the cell membrane somewhat more rigid. Many are able to move about through gliding, but members of the genus Spiroplasma are helical and move by twisting. The best-known genus in the Mollicutes is Mycoplasma. Colonies show the typical "fried-egg" appearance.
Mycoplasmataceae is a family of bacteria in the order Mycoplasmatales. This family consists of the genera Mycoplasma and Ureaplasma.
Acholeplasma are wall-less bacteria in the Mollicutes class. They include saprotrophic or pathogenic species. There are 15 recognised species. The G+C content is low, ranging from 26 - 36% (mol%). The genomes of Acholeplasma species range in size from 1.5 to 1.65 Mbp. Cholesterol is not required for growth. The species are found on animals, and some plants and insects. The optimum growth temperature is 30 to 37 degrees Celsius.
Entomoplasmatales is a small order of mollicute bacteria.
Anaeroplasmatales is an order of mollicute bacteria which are generally found in the rumens of cattle and sheep. The only family in the order is the family Anaeroplasmataceae.
Methanococcus is a genus of coccoid methanogens of the family Methanococcaceae. They are all mesophiles, except the thermophilic M. thermolithotrophicus and the hyperthermophilic M. jannaschii. The latter was discovered at the base of a “white smoker” chimney at 21°N on the East Pacific Rise and it was the first archaeal genome to be completely sequenced, revealing many novel and eukaryote-like elements.
Methanobacteriales is an order of archaeans in the class Methanobacteria. Species within this order differ from other methanogens in that they can use fewer catabolic substrates and have distinct morphological characteristics, lipid compositions, and RNA sequences. Their cell walls are composed of pseudomurein. Most species are Gram-positive with rod-shaped bodies and some can form long filaments. Most of them use formate to reduce carbon dioxide, but those of the genus Methanosphaera use hydrogen to reduce methanol to methane.
In taxonomy, the Methanococcales are an order of the Methanococci.
Thermoproteales are an order of archaeans in the class Thermoprotei. They are the only organisms known to lack the SSB proteins, instead possessing the protein ThermoDBP that has displaced them. The rRNA genes of these organisms contain multiple introns, which can be homing endonuclease encoding genes, and their presence can impact the binding of "universal" 16S rRNA primers often used in environmental sequencing surveys.
Methanomicrobiaceae are a family of archaea in the order the Methanomicrobiales.
Thermofilaceae are a family of archaea in the order Thermoproteales.
In taxonomy, the Thermoproteaceae are a family of the Thermoproteales.
Methanocalculus is a genus of the Methanomicrobiales, and is known to include methanogens.
Mycoplasmatota is a phylum of bacteria that contains the class Mollicutes. The phylum was originally named "Tenericutes". Notable genera include Mycoplasma, Spiroplasma, Ureaplasma, and Candidatus Phytoplasma.
Spiroplasma citri is a bacterium species and the causative agent of Citrus stubborn disease.
Entomoplasma is a mollicute bacteria genus. Entomoplasma freundtii can be isolated from the green tiger beetle.
Mesoplasma is a genus of bacteria belonging to the class Mollicutes. Mesoplasma is related to the genus Mycoplasma but differ in several respects.
The mold, protozoan, and coelenterate mitochondrial code and the mycoplasma/spiroplasma code is the genetic code used by various organisms, in some cases with slight variations, notably the use of UGA as a tryptophan codon rather than a stop codon.
