[Cytochemical and freeze-etching studies of the ultrastructure of a Rickettsiella in a crustacean (author's transl)].

Several characteristics of the intracellular cycle of Ricketsiella are elucidated, particularly regarding the envelope and the cytoplasm of dense forms (elementary bodies) as well as the proteinic inclusions of giant bodies. Cleavage faces have been displayed by freeze-etching, both at the level of cell wall and of plasma membrane. Their characteristics approach those of Gram-negative bacteria and are pratically common to all the stages. Appearance and significance of a polysaccharidic cement joining the outer membrane of the cell wall to the inner membrane (plasma membrane) in the dense forms are discussed. The arrangement of ribosomes and the structure of the nucleoid are described. A 6 nm lattice periodical structure is shown in the proteinic inclusion. Significance of these data for a classification of Rickettsiella and chlamydias is discussed.