Mycoplasmataceae

The family Mycoplasmataceae in the order Mycoplasmatales belongs to the class Mollicutes (the soft-skinned), of cell wall-less prokaryotes. The Mycoplasmataceae are divided into the genera:

• Mycoplasma
• Ureaplasma

Mycoplasmataceae (like almost all representatives of the Mollicutes) have no cell wall, murein is not present. Mycoplasmas are the smallest bacteria that can be cultured in cell-free media, measuring 0.3-0.8 μm. Their genome is very small, about 1/5 of E. coli. Mycoplasma genitalium with 580 kbp has been completely sequenced. Most species are parasites and often pathogenic to humans and animals

Genera and some important species in the family Mycoplasmataceae:

Mycoplasma

• Mycoplasma buccale Freundt et al. 1974
• Mycoplasma salivarum (opportunistic pathogen)
• Mycoplasma pneumoniae (most important human pathogen)
• Mycoplasma fermans (rarely urethritis)
• Mycoplasma genitalium (rarely urethritis)
• Mycoplasma hominis (urethritis)

Ureaplasma

• Ureaplasma urealyticum(urethritis)

The following species are grouped together as urogenital mycoplasmas (about 40% of NGU urethritis is caused by mycoplasmas of the species listed below):

• Ureaplasma urealyticum (60%)
• Mycoplasma hominis (20%)
• Mycoplasma genitalium (15%)
• Mycoplasma fermans (3%)

Peculiarities of mycoplasmas:

• Small size 0,3-0,8um, just microscopically visible
• Can be visualized by Gram stain (Gram positive)
• Small genome size (1/5 of E.coli)
• Main lipid body is cholesterol
• Mycoplasmas do not have the genetic information for the formation of cholesterol. This must be supplied from the outside
• Mycoplasmas do not have a rigid cell wall, thus no characteristic shape. They sometimes appear as balls, drops, rings, discs or threads.
• Mycoplasmas do not have their own nucleotide synthesis
• Mycoplasmas do not have their own amino acid synthesis
• Mycoplasmas do not have their own citric acid cycle
• Mycoplasmas do not produce catalase or peroxidase.

1. Hof H et al (2019) Mycoplasmataceae. In: Hof H, Schlüter D, Dörries R, eds Duale Reihe Medizinische Mikrobiologie. 7th, completely revised and expanded edition. Stuttgart: Thieme p 467-469