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an order of very small microorganisms that differ from true bacteria (Eubacteriae) by the absence of a cell wall. Mycoplasmatales, which are gram-negative, generally nonmotile, and non-sporebearing, are capable of passing through a bacterial filter. In liquid nutrient media they are coccoid, discoidal, or filamentous; on solid media they form small colonies with a dark center. The Mycoplasmatales reproduce by division of threads on coccoid cells. These bacteria are in a number of ways morphologically and physiologically similar to L-form bacteria.
The group of microbes formerly known as pleuropneumonia-like organisms (PPLO) are now assigned to the Mycoplasmatales; they cause pleuropneumonia in cattle and respiratory mycoplasmosis in birds. Mycoplasmatales are also found in humans, causing rheumatic and arthritic conditions and infections of the lacteal glands and respiratory tract. There are saprophytic forms, which live in the mucous membrane of the mouth, as well as in fresh water, sewage, and manure; these forms participate in the breakdown of matter in nature.
REFERENCESTimakov, V. D., and G. Ia. Kagan. Semeistvo Mycoplasmataceae i L-formy bakterii. Moscow, 1967.
Mycoplasmatales and the L-phase of Bacteria. New York, 1969.
A. A. IMSHENETSKII