History of taxonomy Before 1980,
Mycoplasma species (often commonly called "mycoplasmas", now classified as
Mollicutes) were sometimes considered stable
L-form bacteria or even viruses, but
phylogenetic analysis has identified them as bacteria that have lost their cell walls in the course of evolution. The medical and agricultural importance of members of the genus
Mycoplasma and related genera have led to the extensive cataloging of many of these organisms by culture,
serology, and small sub-unit
rRNA gene and whole-genome sequencing. A recent focus in the sub-discipline of
molecular phylogenetics has both clarified and confused certain aspects of the organization of the class
Mollicutes.
Taxonomists once classified
Mycoplasma and relatives in the phylum
Firmicutes, consisting of low G+C
Gram-positive bacteria such as
Clostridium,
Lactobacillus, and
Streptococcus; but modern polyphasic analyses situate them in the phylum
Tenericutes. By the 1990s, it had become readily apparent that this approach was problematic: the
type species,
M. mycoides, along with other significant mycoplasma species like
M. capricolum, is evolutionarily more closely related to the genus
Spiroplasma in the order
Entomoplasmatales than to the other members of the genus
Mycoplasma. As a result, if the group was to be rearranged to match phylogeny, a number of medically important species (e.g.
M. pneumoniae,
M. genitalium) would have to be put in a different genus, causing widespread confusion in medical and agricultural communities. The genus was discussed multiple times by the
International Committee on Systematic Bacteriology's (ICSB) subcommittee on Mollicutes between 1992 and 2011, to no effect. The taxonomy was accepted by the ICSB with validation list 184 in 2018 and became the
correct name. Both
List of Prokaryotic names with Standing in Nomenclature (LPSN) and
National Center for Biotechnology Information (NCBI) now use the new nomenclature. Gupta's proposed taxonomy, as expected, moved the medically important "pneumoniae" group out of
Mycoplasma into its own genus. As a result, a number of mycoplasmologists petitioned to the ICSB to reject the name in 2019. They argue that although Gupta's phylogenetic methods were likely solid, the proposed name changes are too sweeping to be practically adopted, citing some principles of the Code such as "name stability". Gupta and Oren wrote a rebuttal in 2020, further detailing the pre-existing taxonomic problems. In 2022, the ICSP's Judicial Opinion 122 ruled in favor of the name changes proposed by Gupta, meaning they remain valid under the
Prokaryotic Code Gupta
et al. 2019 performed some uncontroversial sorting of the order Mycoplasmatales.
Unassigned species The GTDB and LTP phylogeny above does not include a number of names published under this genus that are either correct or pro-correct according to the LPSN. These species likely belong to a different genus under the standards of the 2018 reorganization, but has not been moved because a new combination has not been proposed, or because the new combination has not been made
valid publication, or because the taxonomic opinion of the LPSN/LoRN refuses to use the new name as the
correct name. The classification of LTP and GTDB is used here to assign a probable target genus. Many new species have been proposed in
Mycoplasma while disregarding the 2018 reorganization; see LPSN for a list. These will be included here and sorted by lineage eventually.
Hemotrophic mycoplasmas: This category includes species that should be moved to
Eperythrozoon under the Gupta reorganization. • "
Ca. M. aoti" Barker et al. 2011 • "
Ca. M. erythrocervae" Watanabe et al. 2010 • "
Ca. M. haematobrackenitadaridae" Becker et al. 2025 • "
Ca. M. haematocervi" corrig. Watanabe et al. 2010 • "
Ca. M. haematodidelphidis" corrig. Messick et al. 2002 • "
Ca. M. haematohominis" corrig. Millán et al. 2015 • "
Ca. M. haematohydrochoeri" corrig. Vieira et al. 2021 • "
Ca. M. haematomacacae" corrig. Maggi et al. 2013 • "
Ca. M. haematominiopteri" corrig. Millán et al. 2015 • "
Ca. M. haematomolossi" Becker et al. 2025 • "
M. haematomyotis" Volokhov et al. 2023 • "
Ca. M. haematonasuae" corrig. Collere et al. 2021 • "
Ca. M. haematoparvum" Sykes et al. 2005 • "
M. haematophyllostomi" Volokhov et al. 2023 • "
Ca. M. haematoselmanitadaridae" Becker et al. 2025 • "
Ca. M. haematosphigguri" corrig. Valente et al. 2021 • "
Ca. M. haematotapirus" Mongruel et al. 2022 • "
Ca. M. haematoterrestris" Mongruel et al. 2022 • "
Ca. M. haematotraderitadaridae" Becker et al. 2025 • "
Ca. M. haematovis" corrig. Hornok et al. 2009 • "
Ca. M. haemobovis" Meli et al. 2010 • "
Ca. M. haemomeles" Harasawa, Orusa & Giangaspero 2014 • "
Ca. M. haemomuris" (Mayer 1921) Neimark et al. 2002 • "
Ca. M. haemoparvum" Kenny et al. 2004 • "
Ca. M. hemominiopterus" Millán et al. 2015 Nested in
Mycoplasmoides: • "
M. bradburyae" Ramírez et al. 2023 – in GTDB Nested in
Mycoplasmopsis: •
M. hafezii Ziegler et al. 2019 – in LTP, close to
Mycoplsmopsis alligatoris •
M. phocimorsus Skafte-Holm et al. 2023 – in LTP, close to "
Mycoplasmopsis elephantis"
Synonimized before 2018 reorganization: • "
M. incognitus" Lo et al. 1989 →
M. fermentans Not in LTP/GTDB, some of which have a 16S in GenBank that can be used to assign the genus: • "
Ca. M. corallicola" Neulinger et al. 2009 –
Mycoplsmopsis (among species mentioned in Gupta et al. (2018), "
Mycoplsmopsis iguanae" was the highest 16S BLAST hit) • "
Ca. M. coregoni" corrig. Rasmussen et al. 2021 • "
Ca. M. didelphidis" corrig. Pontarolo et al. 2021 • "
M. insons" May et al. 2007 • "
Ca. M. kahanei" Neimark et al. 2002 • "
M. monodon" Ghadersohi & Owens 1998 • "
M. pneumophila" Lyerova et al. 2008 • "
Ca. M. ravipulmonis" Neimark, Mitchelmore & Leach 1998 • "
Ca. M. salmoniarum" corrig. Rasmussen et al. 2021 • "
M. sphenisci" Frasca et al. 2005 • "
M. timone" Greub & Raoult 2001 • "
Ca. M. tructae" Sanchez et al. 2020 • "
Ca. M. turicense" corrig. Willi et al. 2006 • "
M. volis" Dillehay et al. 1995 • "
M. vulturii" Oaks et al. 2004 == Synthetic mycoplasma genome ==