Membranous inclusions of Pseudomonas aeruginosa.

Electron microscopy of sectioned cells of Pseudomonas aeruginosa treated with a double fixative in N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid revealed a number of membranous inclusions varying in size and morphology. One round, electron transparent form was frequently observed which did not routinely appear to be attached to the cytoplasmic membrane and varied in size from 120 to 300 nm in diameter. However, in one case, several tubular structures between an inclusion and the cytoplasmic membrane was observed. On rare occasions, a large and unusual multilayered inclusion consisting of three thick and distinct layers was also encountered. In addition, two small mesosomal structures were singly observed in cells and were situated proximal to the cytoplasmic membrane. One type appeared to consist of a single thin membrane, whereas the other type consisted of a delicate, multilayered structure.