| Abstract: | In cells of the stable and unstable spheroplast type L-form of Proteus mirabilis D 52 small ellipsoidal particles (SE-particles) could be found after investigation of ultrathin sections. The SE-particles have diameters of 220–260 and 280–320 Å. They are composed of an electron lucent centre, an internal electron deanse layer, an electron lucent line and an outer electron dense layer. There is a porus of about 25 Å in the internal electron dense layer. The SE-particles may be arranged in chains up to 10 particles. It seems that the particle formation starts near the cytoplasmic membrane at one or more sites in a cell. Comparing electron microscopic observations with data from literature it seems certain that SE-particles are bacteriophage-like structures. However, it is not clear until now, whether they are intact tail-less phages or defect phage structures. |
