The structure of Mycoplasma pneumonia is very unique and infinitely interesting. Besides the fact M. pneumonia is one of the smallest free living organisms known, they also lack a cell wall and still maintain cell rigidity.
The key to M. pneumoniae’s ability to maintain regular cell morphology is the presence of a fibrous cytoskeleton deep to the cell membrane. The cytoskeleton is made up many different fibrous proteins. Each “fiber” is 80-100 wide by 250-300nm long. The proteins that make up the cytoskeleton are diverse in function. Some of these functions include: support, motility, translation, heat shock response, energy metabolism, and attachment to host cells. In addition to these proteins, a few lipoproteins can also be found in the cytoskeleton. The protein thought to be responsible for motility in M. pneumoniae is the “Neimark protein”. The Neimark protein is much like the actin molecule found in the muscle of many animals and is thought to function much the same. Other important proteins found in the cytoskeleton include the so called “adhesion proteins”. These proteins are responsible for the binding of the M. pneumoniae cell to the host cells. The adhesion proteins include the P30 protein, P40 protein, and P90 protein. Without the presence of any of these proteins, the M. pneumoniae cells cannot bind to host cells. These proteins work in conjunction with the "attachment organelle" to bind to host cells. The attachment organelle is also thought to play a major role in reproduction. M. pneumoniae reproduces via binary fission.
Surrounding the cytoskeleton is the plasma membrane. Unlike the lipid bi-layer of most organisms, M. pneumoniae has a tri-layered cell membrane that contains serol-like molecules that function to add support.