The term "mycoplasma", from the Greek μύκης, mykes (fungus) and πλάσμα, plasma (formed), was first used by Albert Bernhard Frank in 1889 to describe an altered state of plant cell cytoplasm resulting from infiltration by fungus-like microorganisms.

[4][5] Julian Nowak later proposed the name mycoplasma for certain filamentous microorganisms imagined to have both cellular and acellular stages in their lifecycles, which could explain how they were visible with a microscope, but passed through filters impermeable to other bacteria.

[7] At present, all these organisms are classified as Mollicutes, and the term Mycoplasma solely refers to the genus.

[citation needed] Species of Mycoplasma, other than those listed below, have been recovered from humans, but are assumed to have been contracted from a non-human host.

[9] Dietary nitrogen availability has been shown to alter codon bias and genome evolution in Mycoplasma and the plant parasites Phytoplasma.

[7] Due to the lack of a rigid cell wall, Mycoplasma species (like all Mollicutes) can contort into a broad range of shapes, from round to oblong.

[12] In 1954, using phase-contrast microscopy, continual observations of live cells have shown that Mycoplasma species ("mycoplasmas", formerly called pleuropneumonia-like organisms, PPLO, now classified as Mollicutes) and L-form bacteria (previously also called L-phase bacteria) do not proliferate by binary fission, but by a uni- or multi-polar budding mechanism.

Microphotograph series of growing microcultures of different strains of PPLOs, L-form bacteria and, as a control, a Micrococcus species (dividing by binary fission) have been presented.

[15] 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.

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.

A total of 78 species were removed from Mycoplasma, creating five new genera and a number of higher taxonomic levels.

[21] Gupta's proposed taxonomy, as expected, moved the medically important "pneumoniae" group out of Mycoplasma into its own genus.

[34] Mycoplasma cells are physically small – less than 1  μm, so are difficult to detect with a conventional microscope.

A Corning study showed that half of U.S. scientists did not test for Mycoplasma contamination in their cell cultures.

[39] A chemically synthesized genome of a mycoplasmal cell based entirely on synthetic DNA which can self-replicate has been referred to as Mycoplasma laboratorium.

[44] In addition, infection is associated with increased risk of cervicitis, infertility, preterm birth and spontaneous abortion.

[49] Cells infected with Mycoplasma for an extended period of time show significant chromosomal abnormalities.

[citation needed] The malignant transformation induced by Mycoplasma species is also different from that caused by other pathogens in that the process is reversible.

The window of time when reversibility is possible varies greatly; it depends primarily on the Mycoplasma involved.

[49] If the bacteria are killed using antibiotics[49] (i.e. ciprofloxacin[48] or Clarithromycin[58]) before the irreversible stage, the infected cells should return to normal.

Epidemiologic, genetic, and molecular studies suggest infection and inflammation initiate certain cancers, including those of the prostate.

M. genitalium and M. hyorhinis induce malignant phenotype in benign human prostate cells (BPH-1) that were not tumorigenic after 19 weeks of exposure.