- A-Z
- Endocytobiosis and ...
- Volume 6
- Issue 2-3
- Endocytobiosis in B...
- Autor(in)
- Seitenbereich
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121 - 147
- Zusammenfsg.
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The cockroach Blattella germanica (Blattodea) hosts symbiotic bacteria in both the fat body and the ovary. Bacteria have the typical cell boundary profile of Gram-negative microorganisms and are encapsulated by a vacuolar membrane produced by the bacteriocyte. Our data indicate that the origin of the bacteriocytes should be looked for in the cells of the hemocyte line, especially in the embryonic plasmatocytes. These cells, that we call pre-bacteriocytes, interacting with the prokaryote symbionts, initiate a series of structural and functional modifications that lead to the differentiation of the bacteriocytes. The bacteria are inside vacuoles of endocytosis, with which lysosomes do not fuse and thus no digestive vacuoles are formed. This process is probably under the control of the bacteria, and permits a rapid increase in the number of the initial symbiotic population. A functional and genetical integration of the prokaryote symbiont with the eukaryotic host cell is thus allowed. The symbionts are involved in many complex physiological processes of the host organism. We have demonstrated, by E.M. and freeze-fracture preparations, the presence of vesicles arising from the vacuolar membrane and projecting towards the symbionts, close adhesion sites between the vacuolar membrane and the envelope of the symbiont, and aggregates of IMPs in the freeze-fracturated vacuolar membrane. In Blattella germanica there is a transovarian transmission of the symbiotic population to the progeny. Our data enable us to describe the sequence of the bacterial penetration into the oocyte. The symbiotic bacteria, at the end of the vitellogenesis, when the microvillar border of the oolemma is disappeared, make contact with the egg surface and are taken in the egg periplasm. Our preliminary researches show, in the 1-day-old embryo, the presence of a second covering around the vacuole of endocytosis. This microtubule-like structure could be involved in a passive transfer of the bacteria to the center of the yolk.