Abstract
Electron microscopy of thin sections of two mosqulto-toxic isolates ofBacillus thuringiensis H-14 showed inlcusions that varied in shape, size and stainability. The shape of some of these inclusions have not been reported before. Uitrastructural analysis of sporulation and parasporal crystal development shows that the insecticidal inclusions are initiated at the stage of axial filament formation during sporulation. In most of the inclusions there is a common subunit, formed first, which has a regular geometrical shape (rhomboid, hexagonal rectangular, trapezoid or pentagonal). Later added sub-units are more amorphous and this leads to a variety of inclusion shapes which appear at the end of sporulation. Some of these reguiar moleties develop in different ways, leading to cubical, rhomboid or parallelogramic-shaped crystais. In a freeze-tractured cell, the internal fracture faces of a crystal are seen. The size of the sub-units of this crystal was about 5×5 nm. For French summary, see next page.
Résumé
La microscopie électronique de sections minces de deux isolates deBacillus thurigiensis H-14, toxiques pour les moustiques révèle des inclusions de forme, de taille et de comportement à la coloration variables. La forme de certaines de ces inclusions n'a pas été rapportée auparavant. L'analyse ultrastructurale de la sporulation et du développement cristallin parasporal montre que les inclusions insecticides sont initiées au stade de la formation des filaments axiaux pendant la sporulation. Dans la plupart de ces inclusions, il y a une sous-unité commune formée d'abord, qui a une forme géométrique régulière (rhomboïde, hexagonale, reclangulaire, trapézoïdale ou pentagonale). Les sous-unités ajoutées par la suite sont plus amorphes et ceci conduit a une variété de forme des inclusions qui apparaît à la fin de la sporulation. Certaines de ces parties régulières se développent de diverses manières ce qui conduit à des cristaux cubiques, rhomboïques ou de forme parallélogramique. On peut voir les faces internes du cristal dans les cellule fracturées sous gel. La taille des sousunités de ce cristal était de 5 nm sur 5 nm environ.
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Abdel-Hameed, A., Lounatmaa, K., Carlberg, G. et al. Studies onBacillus thuringiensis H-14 strains isolated in Egypt—II. Ultrastructure studies. World J Microbiol Biotechnol 6, 305–312 (1990). https://doi.org/10.1007/BF01201302
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DOI: https://doi.org/10.1007/BF01201302