pleuropneumonia-like organism

biology

Also known as: PPLO

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Last updated

July 19, 2026

Quick Summary

Pleuropneumonia-like organisms (PPLOs) are a type of bacterium belonging to the genus Mycoplasma. These are among the smallest known bacterial organisms, lacking cell walls and varying in shape from spherical to filamentous.1

PPLOs are parasites that inhabit the mucous membranes of the respiratory, genital, or digestive tracts in various animals, including humans. They can cause illness by accumulating toxic byproducts in host tissues. Mycoplasma pneumoniae, for instance, is a cause of pneumonia in humans.1

These organisms are so small that they can only be seen with a high-powered electron microscope. Their minimal size means they rely heavily on the host's tissues for survival and necessary biological functions.2

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life
Sizes of organisms
…smallest free-living cells include the pleuropneumonia-like organisms (PPLOs). Whereas an amoeba has a mass of 5 × 10⁻⁷ gram (2 × 10⁻⁸ ounce), a PPLO, which cannot be seen without a high-powered electron microscope, weighs 5 × 10⁻¹⁶ gram (2 × 10⁻¹⁵ ounce) and is only about 100 nanometres across.…
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…smallest free-living cells include the pleuropneumonia-like organisms (PPLOs). Whereas an amoeba has a mass of 5 × 10⁻⁷ gram (2 × 10⁻⁸ ounce), a PPLO, which cannot be seen without a high-powered electron microscope, weighs 5 × 10⁻¹⁶ gram (2 × 10⁻¹⁵ ounce) and is only about 100 nanometres across.…
Read More