Effect of Bacillus thuringiensis beta exotoxin on ultrastructures of midgut cells of Culex sitiens.

In midgut cells of Culex sitiens intoxicated with beta exotoxin of Bacillus thuringiensis, the microvilli are greatly reduced. In the cytoplasm there is progressive disarrangement of the membranes of the rough endoplasmic reticulum, first to spherules, and later to a granular mass. Minute vacuoles appearing in the cytoplasm are parts of the distorted labyrinth and remains of the Golgi membranes. There is no disintegration of the outer cell membrane, and no hypertrophy of goblet cells. Nuclei remain in their posterior position and there are no cytoplasmic autophagic vacuoles in the centre. Cells in the same part of the midgut differ in the degree of disorganization.