23-459: Acholeplasmatales Anaeroplasmatales Entomoplasmatales Haloplasmatales Mycoplasmatales Mollicutes is a class of bacteria distinguished by the absence of a cell wall . The word "Mollicutes" is derived from the Latin mollis (meaning "soft" or "pliable"), and cutis (meaning "skin"). Individuals are very small, typically only 0.2–0.3 μm (200–300 nm ) in size and have
46-405: A member of the genus Mycoplasma . Analysis of the genomes of Mollicutes ("mycoplasmas") gives solid support for the hypothesis that Mollicutes have developed from Gram-positive bacteria by a process of reductive evolution. By adopting a parasitic mode of life with use of nutrients from their hosts, many Mollicutes were able to reduce their genetic material considerably. On the other hand, they lost
69-530: A monophyletic origin for the Mollicutes within the Bacillota. An early edition of Bergey's Manual of Systematic Bacteriology placed class Mollicutes within phylum Bacillota , whereas in the announced 2nd edition, they are moved to a separate phylum Tenericutes (later renamed Mycoplasmatota ). The change is motivated by "their unique phenotypic properties, in particular the lack of rigid cell walls, and
92-1094: A third order, Anaeroplasmatales , taking into account that dependence on anaerobic growth conditions is an important characteristic. The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN) and National Center for Biotechnology Information (NCBI) Mycoplasma feliminutum Heyward, Sabry & Dowdle 1969 Haploplasma Mariniplasma Alteracholeplasma Paracholeplasma Anaeroplasma Acholeplasma " Ca. Pelethenecus " Gilroy et al. 2021 Anaeroplasma Robinson, Allison & Hartman 1975 [" Ca. Avacholeplasma" Gilroy et al. 2021 ] Paracholeplasma Watanabe et al. 2021 Mariniplasma corrig. Watanabe et al. 2021 Haploplasma Watanabe et al. 2021 Acholeplasma Edward & Freundt 1970 Alteracholeplasma Watanabe et al. 2021 " Ca. Phytoplasma " Firrao et al. 2004 Mycoplasmatales Mycoplasmataceae
115-428: 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. Mollicutes are parasites of various animals and plants, living on or in
138-510: Is a family of bacteria . It is the only family in the order Acholeplasmatales , placed in the class Mollicutes . The family comprises the genera Acholeplasma and Phytoplasma . Phytoplasma has the candidatus status, because members still could not be cultured. Etymology : The names Acholeplasmataceae and Acholetoplasmatales are derived from the Greek a = not, cholè = bile and plasma = anything moulded or formed. Species in
161-583: Is a family of bacteria in the order Mycoplasmatales. This family consists of the genera Mycoplasma and Ureaplasma . In 1967, the order Mycoplasmatales was incorporated into the class Mollicutes. Many species are sexually transmitted and cause pelvic inflammatory disease . Mycoplasma is a genus of bacteria that lack a cell wall and possess a three-layered cellular membrane. They can be parasitic or saprotrophic . Several species are sexually transmitted and pathogenic in humans. Others are found on cats, dogs, and barnyard fowl. Ureaplasma
184-631: Is the second of two genera of bacteria belonging to the family Mycoplasmataceae. As the name implies, ureaplasma is urease positive. This genera is distinct from other genera in Mollicutes in that it hydrolyses urea for generation of ATP. Both Ureaplasma urealyticum and Ureaplasma parvum have been identified as important human pathogens, causing infection in the urogenital tract and, rarely, at distal sites. Their role in neonatal disease and adverse pregnancy outcomes has been well established, and semantic classifications are changing to reflect
207-1027: The "kingdom" (now domain ) Bacteria into three divisions (= phyla) on the basis of the cell wall types: For classification and nomenclature of Mollicutes, there are special rules, which are maintained by the International Committee on Systematics of Prokaryotes (ICSP) Subcommittee on the Taxonomy of Mollicutes (formerly the International Committee on Systematic Bacteriology (ICSB) Subcommittee on taxonomy of Mycoplasmatales ). Traditionally, Mollicutes taxonomy has been based on serology and phenotypic characteristics . However, most modern classifications are based on DNA or RNA sequences, especially 16S rRNA sequences (see Figure). The results of Mollicutes phylogenetic analyses have been controversial. Some taxonomists place them in Bacillota, others in Mycoplasmatota. Woese et al. suggested that
230-464: The 1980s. Research in women has lagged several decades behind, but it is now becoming more clear how Ureaplasma spp. contribute to etiologies such as interstitial cystitis / painful bladder syndrome . Ureaplasma spp. are associated with alterations in host environment that increase susceptibility to other infections such as bacterial vaginosis and vaginal candidiasis . Ureaplasma spp. can cause reactive arthritis as well as directly infect
253-646: The Mollicutes have developed rather sophisticated mechanisms to colonize their hosts and resist the host immune system. Mollicutes (formerly also called pleuropneumonia-like organisms, PPLO) as well as L-form bacteria (formerly also called L-phase bacteria), both lacking cell walls, do not proliferate by binary fission but by a budding mechanism. In 1954, this mode of proliferation has been shown by continual observations of live cells using phase-contrast microscopy. Previously, Mollicutes were sometimes considered stable L-form bacteria, but phylogenetic analysis has identified them as bacteria that have lost their cell walls in
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#1732798106067276-603: The Mollicutes might have been derived from different branches of bacteria. They concluded, that the Mollicutes are not a phylogenetically coherent group and therefore do not form a distinct higher level taxon. Instead, they cluster within Gram-positive bacteria of the phylum Bacillota. The results of molecular phylogenetic analyses have been partly dependent on the chosen molecular marker, like rRNA , elongation factor or another protein. Phylogenetic trees based on phosphoglycerate kinase (Pgk) amino acid sequences' indicated
299-495: The Mycoplasmata. Now, the name Mycoplasma should exclusively be used for members of the genus Mycoplasma , rather than the use as a trivial name for any Mollicute. As the trivial name has been used in literature for a long time, this is yet not always the case. Traditionally, the taxonomy of bacteria was based on similarities and differences in morphology (Linnaean taxonomy). In 1962, R.G.E. Murray proposed to divide
322-474: The causative organism of bovine pleuropneumonia and referring to the pleuropneumonia-like organisms. Until then, Mycoplasma mycoides was known as Asterococcus mycoides , but later that name was not recognized as valid. In their publication of 1956, they described 15 species of Mycoplasma . In 1967 the class Mollicutes, containing the order Mycoplasmatales , was proposed by the Subcommittee on Taxonomy of
345-639: The course of evolution. The classification of the Mollicutes has always been difficult. The individuals are tiny, and being parasites, they have to be cultivated on special media. Until now, many species could not be isolated at all. In the beginning, whether they were fungi, viruses, or bacteria was not clear. Also, the resemblance to L-forms was confusing. At first, all members of the class Mollicutes were generally named "mycoplasma" or pleuropneumonia-like organism (PPLO). Mollicutes other than some members of genus Mycoplasma were still unidentified. The first species of Mycoplasma /Mollicutes, that could be isolated
368-1212: The general low support by alternative markers". In the Taxonomic Outline of Bacteria and Archaea (TOBA Release 7.7), March 2007, the Mollicutes are a class in the phylum Bacillota. The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN) and National Center for Biotechnology Information (NCBI) other Lottiidibacillus Culicoidibacter Haloplasma ♦ Turicibacter other Fusobacteriales Asteroleplasma ♦ Coprobacillaceae Erysipelotrichaceae ♦ Acholeplasmataceae (incl. Anaeroplasmataceae ) Metamycoplasmataceae Spiroplasma species-group 3 Mycoplasmoidaceae Spiroplasma { Spiroplasmataceae } Spiroplasma species-group 2 " Edwardiiplasma " Entomoplasmataceae Mycoplasmataceae other "Staphylococcales" Culicoidibacter Turicibacter Haloplasma ♦ " Ca. Bathoplasma " [MAG-NZ] "Hujiaoplasmataceae" "Izemoplasmataceae" Anaeroplasmataceae UBA5453 Acholeplasmataceae "Aphodocolaceae" [RF39] "Caccosomataceae" Acholeplasmataceae Acholeplasmataceae
391-417: The genes for many assimilative processes. Thus, Mycoplasma possibly became the smallest self-replicating organism in nature. Mycoplasma genitalium , with 580,000 base pairs, has an especially small genome size. Some phytoplasmas also have a very small genome size. The genera with the smallest genome are considered to be phylogenetically the most "recent" mollicutes. To maintain their parasitic mode of life
414-440: The host's cells. Many cause diseases in humans, attaching to cells in the respiratory or urogenital tracts, particularly species of Mycoplasma and Ureaplasma . Phytoplasma and Spiroplasma are plant pathogens associated with insect vectors. Whereas formerly the trivial name "mycoplasma" (plural: "mycoplasmas") has commonly denoted any member of the class Mollicutes, it now in scientific classification refers exclusively to
437-566: The nature of the detrimental outcomes these infections are associated with. In the 2010s, Mycoplasma genitalium has been re-classified as an STI , and it is possible that with more research, Ureaplasma spp . will follow this trend. Similar to other pathogens such as Chlamydia trachomatis , infection with Ureaplasma spp. is associated with adverse fertility outcomes in both men and women. Both cause non-gonococcal urethritis . Ureaplasma spp. were implicated in conditions such as prostatitis and chronic pelvic pain syndrome as early as
460-457: The order Acholeplasmatales can grow in a medium without cholesterol, unlike species in the order Mycoplasmatales . Cholesterol , a sterol , is an important component of the cell membrane of mycoplasmas, whereas in acholeplasmas and in bacteria in general it is absent. Members of Acholeplasmatales are facultative anaerobic . They are parasites or commensals of vertebrates, insects, or plants; some are saprophytes . Phytoplasmas colonize
483-524: The phloem sieve elements of vascular plants , causing diseases. They are transmitted by sap-sucking insects (primarily leafhoppers , planthoppers , and psyllids ), living in the gut, haemolymph, salivary gland and other organs. Like other mollicutes, they show a high host specificity . In the first taxonomy of Mollicutes, the classification was based on requiring or not requiring cholesterol for growth. The old order Mycoplasmatales consisted of two families: Mycoplasmataceae , which requires cholesterol, and
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#1732798106067506-480: The sterol-nonrequiring Acholeplasmataceae. In view of the many properties in which the acholeplasmas distinguish from species in Mycoplasmataceae and Spiroplasmataceae, Freundt et al. proposed in 1984 to elevate the family Acholeplasmataceae to the ordinal rank Acholeplasmatales, thus separating it from Mycoplasmatales. In 1987, the division in sterol requiring and not requiring changed with the addition of
529-513: Was Mycoplasma mycoides . This bacterium was cultivated by Nocard and Roux in 1898. In 1956, D.G. Edward and E.A. Freundt made a first proposal for classifying and naming PPLOs. They left undecided, however, whether they belong to the bacteria ( prokaryotes , in 1956 called "Schizomycetes") or to the eukaryotes . As type species (name-giving species) of the PPLOs/mycoplasmas, Edward and Freundt proposed Mycoplasma mycoides , being
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