Membrane systems in endocytobiosis I. Specializations of the vacuolar membrane in bacteriocytes of Blattella germanica (L.) (Dictyoptera: Blattellidae)

In bacteriocytes of Blattella germanica the symbionts are enveloped by the vacuolar membrane which is produced by the eukaryotic host cell. A study of serial thin sections shows the presence of vesicles originated from a blebbing process of the vacuolar membrane. Also, the presence of close adhesion sites between the vacuolar membrane and the prokaryotic cell envelope is revealed. Freeze-fracture replicas evidence aggregates of intramembrane particles on the vacuolar membrane while no corresponding membrane differentiation is present on the symbiont cell envelope. These observations are discussed in relation to the peculiarity of the interaction which involves both eukaryotic and prokaryotic cell membranes.