Mycoplasmas are group of bacteria those do not have cell wall and are highly pleomorphic, with no fixed shape or size. They do not have even cell wall precursors like muramic acid or diaminopimelic acid.
While considering size, mycoplasmas are the smallest free – living microorganisms, and one of the most pleomorphic.
Mycoplasmas do not possess spores, flagella or fimbriae. Few of them exhibit a gliding motility. Mycoplasmas are Gram negative but are better stained by Giemsa stain.
Mycoplasmas may be cultivated in fluid or solid media. They are generally facultative anaerobes, growth being better aerobically. Temperature for its good growth range from 22 – 41 C, the parasitic species growing optimally at 35 – 37 C and the saprophytes at lower temperatures.
For cultivation of mycoplasmas, media is added with horse or human serum and yeast extract. Penicillin and thallium acetate are added as selective agents.
Colonies appear is typically biphasic, with ‘fried egg’ appearance, consisting of a central opaque granular area of growth extending into the depth of the medium, surrounded by a flat, translucent peripheral zone.
Mycoplasmas are parasites of humans, animal, plants, or arthropods. They are typically found on the mucous surface of the respiratory and urogenital tracts of human and animals. Although some of mycoplasmas belong to the normal flora, many species are pathogens and cause various diseases.
Most of mycoplasmas those infect human and other animals are surface parasites. They mainly found adhering to the epithelial lining of the respiratory and urogenital tracts.
The mycoplasmas are very sensitive to tetracyclines, macro lines, and the newer quinolones, but they are resistant to antibiotics that specifically inhibit bacterial cell wall synthesis (as mycoplasmas do not have a cell wall). Tetracycline or erythromycin is recommended for treatment of M. pneumoniae pneumonia.