Mycoplasma species are the smallest free-living organisms. These organisms
are unique among prokaryotes in that they lack a cell wall, a feature largely
responsible for their biologic properties such as their lack of a reaction to
Gram stain and their lack of susceptibility to many commonly prescribed
antimicrobial agents, including beta-lactams. Mycoplasmal organisms are usually
associated with mucosal surfaces, residing extracellularly in the respiratory
and urogenital tracts. They rarely penetrate the submucosa, except in the case
of immunosuppression
or
instrumentation, when they may invade the
bloodstream and disseminate to different
organs
and tissues throughout the body.
Without a cell wall, they are unaffected
by many common antibiotics such as penicillin or other beta-lactam antibiotics that target cell wall synthesis. They can be parasitic or
saprotrophic. Several species are pathogenic in humans, including M. pneumoniae, which is an
important cause of a typical pneumonia and other respiratory disorders, and M. genitalium, which is believed to be involved in pelvic inflammatory diseases. Mycoplasma species are the smallest bacterial
cells yet discovered, can survive
without oxygen, and come in various shapes. For example, M. genitalium is flask-shaped (about 300 x 600 nm), while M.
pneumoniae is more elongated
(about 100 x 1000 nm). Hundreds of mycoplasma species infect
animals
The origin of the name-
The
term mycoplasma, from the
Greek word - mykes (fungus) and 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. Julian Nowak later proposed the genus name Mycoplasma for certain filamentous microorganisms
imagined to have both cellular and acellular stages in their life cycles, which
could explain how they were visible with a microscope, but passed through
filters impermeable to bacteria. Later, the name for Mycoplasma was pleuropneumonia-like
organisms (PPLO), broadly
referring to organisms similar in colonial morphology and filterability to the
causative agent (a mycoplasma) of contagious
bovine pleuropneumonia
Characteristics
Over 100
species have been included in the genus Mycoplasma.
Microbes of the class Mollicutes, to which Mycoplasma
belongs, are parasites or commensals of humans, animals, and plants. the genus Mycoplasma uses vertebrate and arthropod hosts. Dietary
nitrogen availability has been shown to alter codon bias and genome evolution
in Mycoplasma and Phytoplasma
Cell morphology "Due
to the lack of a rigid cell wall, Mycoplasmataceae can contort into a broad
range of shapes, from round to oblong. They therefore cannot be classified as
rods or cocci.
