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Taxonomy of mollicutes (mycoplasmas)

The Taxonomy of mollicutes (mycoplasmas)

Fig. 1. The new taxonomy of the mollicuts (Mycoplasmas). Red taxa represent new names. Green names represent taxa where the names have not been changed and which belong to the same higher taxon as before. Yellow names represent taxa where the names have not been changed, but which have been placed within another higher taxon than before. Genera of importance within veterinary medicine are underlined. Note that all higher taxa within the phylum Tenericutes are not included in this figure. - Click on the image to enlarge it.

Taxonomy of mollicutes (mycoplasmas)

Fig. 2. Species of mollicutes (mycoplasmas) with importance for veterinary medicine. At the top of each box is the name of the different genera and below the genus name follow the different species names. The same color coding is used in Fig. 2 as in Fig. 1. All species in the figure are included in VetBact, but A. laidlawii does not have much veterinary significance. - Click on the image to enlarge it.

Introduction

The taxonomy of mollicutes (mycoplasmas) has previously been controversial because it has not reflected their phylogeny, i.e. their natural relations. A Canadian and an Israeli research group have now carried out a comprehensive study based on whole-genome sequencing, where a thorough revision of the taxonomy of the mollicutes has also been proposed (see reference below).

The revised taxonomy

In the revised taxonomy, a new order has been introduced, namely Mycoplasmoidales, which includes the new families Myco­plasmoidaceae and Metamycoplasmataceae. The family Mycoplasmoidaceae contains the new genera Malacoplasma and Mycoplasmoides as well as the genera Eperythrozoon and Ureaplasma. The genus Eperythrozoon was previously tried to be transferred to the genus Mycoplasma, when it was understood that these organisms are not rickettsiae. However, the genus name Eperythrozoon has priority and therefore these organisms should still have the original genus name, even though they belong to the class Mollicutes. The family Meta­mycoplasmataceae contains the new genera Meso­mycoplasma, Meta­mycoplasma and Myco­plasmopsis.

The only previously called mycoplasmas, which still belong to the order Mycoplasmatales, are those that belong to the so-called the mycoides group. This is good, because in that group one finds the most important "mycoplasmas" from a veterinary and global point of view. Now you should only use the term "mycoplasma" as a trivial name if you are referring to organisms, which belong to the revised genus Mycoplasma. Otherwise, the term "mollicutes" should be used. The genera Spiro­plasma, Entomoplasma and Mesoplasma formerly belonged to the order Entomoplasma­tales. However, to emphesize the close relationship with the  mycoplasmas of the mycoides group, they should be affiliated to the order Mycoplasmatales. The genera Spiroplasma, Entomoplasma and Mesoplasma have hardly any significance in veterinary medicine, but the latter two should perhaps be placed in the two families (Entomo­plasma­taceae and Meso­plasmataceae, respectively) under the order Mycoplasma­tales.

Summary

The new taxonomy for the mollicutes will probably create some misunderstandings and cause confusion because the five new family names are so similar to each other. In the long run, however, the new taxonomy will be a support for those who are interested in the connections between the various organisms within this interesting bacterial group.

References

Gupta RS, Sawnani S, Adeolu M et al. 2018. Phylogenetic framework for the phylum Tenericutes based on genome sequence data: proposal for the creation of a new order Mycoplasmoidales ord. nov., containing two new families Mycoplasmoidaceae fam. nov. and Metamycoplasmataceae fam. nov. harbouring Eperythrozoon, Ureaplasma and five novel genera. Antonie van Leeuwenhoek 111:1583–1630.

Updated: 2021-11-25.


News

The revised taxonomy of the mollicutes

The revised taxonomy of mollicutes (mycoplasmas) has now been introduced on VetBact, which means that many of the species have been given new genus names or moved to another higher taxon. 

Published 2021-11-25. Read more...

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