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Scientific classification
Kingdom: Bacteria
Phylum: Firmicutes or


Class: Mollicutes
Order: Acholeplasmatales
Family: Acholeplasmataceae

Ca. Phytoplasma

The Acholeplasmatales are an order in the class Mollicutes, containing only one family, Acholeplasmataceae, comprising the genera Acholeplasma and Phytoplasma. Yet, Phytoplasma has the Candidatus state, because members still could not be cultured.

Etymology: The name Acholeplasmatales is derived from the Greek a = not, cholè = bile and plasma = anything moulded or formed. [1]
Species in 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. [2]

Phytoplasmas colonize the phloem sieve elements of vascular plants, causing diseases. They are transmitted by sap-sucking insects (primarily leafhoppers, planthoppers, and psyllids [3] ), living in the gut, haemolymph, salivary gland and other organs. Like other mollicutes, they show a high host specificity. [4]


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 the sterol-nonrequiring Acholeplasmataceae. [1][5] 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. [6]

In 1987, the division in sterol requiring and not requiring changed with the addition of a third order, Anaeroplasmatales, taking into account that dependence on anaerobic growth conditions is an important characteristic. [7]


  1. 1.0 1.1 D.G. Edward, E.A. Freundt Amended nomenclature for strains related to Mycoplasma laidlawii.; J Gen Microbiol. 1970 Jul; 62; PDF
  2. Stephens et al. Intraspecies Genetic Relatedness among Strains of Acholeplasma laidlawii and of Acholeplasma axanthum by Nucleic Acid Hybridization J. of General Microbiology (1983), 129, p 1929-1934.
  3. Phyllis G. Weintraub and LeAnn Beanland Insect vectors of phytoplasmas Annual Review of Entomology; Vol. 51: 91-111 (2006); doi:10.1146/annurev.ento.51.110104.151039
  4. IRPCM Phytoplasma/Spiroplasma Working Team ‘Candidatus Phytoplasma’, a taxon for the wall-less, non-helical prokaryotes that colonize plant phloem and insects; Int J Syst Evol Microbiol 54, 1243–1255 (2004).
  5. Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  6. Freundt et al. Proposal for elevation of the family Acholeplasmataceae to ordinal rank: Acholeplasmatales. Int. J. Syst. Bacteriol., 1984, 34, 346-349.
  7. I.M. Robinson and E.A. Freundt Proposal for an Amended Classification of Anaerobic Mollicutes Int J Syst Bacteriol 1987, Vol. 37, p. 78-81