A wall-less bacterium that causes chest colds and the mild pneumonia people often keep walking around with. Explore its illustrative 3D model, human context, and sources.
PHAC describes M. pneumoniae as a spindle-shaped, pleomorphic bacterium measuring 1 to 2 micrometres long by 0.1 to 0.2 micrometres wide that lacks a cell wall, has a three-layered membrane containing sterols for structural support, and uses gliding motility instead of pili or flagella. CDC states that the bacteria cause respiratory tract infections and can damage the lining of the throat, windpipe and lungs, that the most common presentation is a chest cold while pneumonia is less common, and that it can take 1 to 4 weeks for symptoms to appear after exposure. Having no cell wall is the reason cell-wall antibiotics such as penicillins do not work against it. PHAC describes cyclic epidemics every 3 to 6 years.
CDC describes the usual illness as a chest cold, with pneumonia less common and often mild enough to be called walking pneumonia. PHAC records that extrapulmonary complications including encephalitis, aseptic meningitis and Guillain-Barré syndrome occur, and that skin manifestations such as Stevens-Johnson syndrome are reported in up to 25% of infections in its account. Those complication figures describe reported series, not the chance that a given chest cold becomes severe.
Mycoplasma pneumoniae · One tapered, wall-less spindle with a terminal attachment organelle; pleomorphic cells can look different. This is a species-informed teaching diagram; colours, proportions, envelope spacing and internal detail are illustrative. The model uses muted illustrative colours; stains, colony pigments and microscopy colourization are not natural cell colours. Anatomy is enlarged for phone viewing. Morphology reference: Mycoplasma pneumoniae · pathogen safety data sheet.
Source check: 2026-09-20. Educational content; independent scientific review remains pending.