Mycoplasma pneumoniae. Coloured Transmission Electron Micrograph (TEM) of a section through cells of Mycoplasma pneumoniae. At centre is a dumb-bell shaped cell with cell contents appearing granular (red), and two cells are at upper left. Mycoplasmas are the smallest cellular organisms known (diameter 0.3-0.9 microns). In some respects they are similar to primitive bacteria. They are different in that they lack a true cell wall, and so display a variety of forms (as seen here). Mycoplasma pneumoniae causes a pneumonia-like disease in humans. Other species of Mycoplasma infect the respiratory tract of cattle, sheep and goats. Magnification: x71,000 at 6x4.5cm size. Mag. x300,000 at 8x10 inch size.