Ultrastructural Effects of Bacillus thuringiensis var. san diego on Midgut Cells of the Cottonwood Leaf Beetle1
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Journal of Inverterbrate Pathology. Vol. 60 no. 1.:p. 15-25 (1992)
Sequential observations of the ultrastructural effects of Bacillus thuringiensis var. san diego were made on midgut epithelial cells of the cottonwood leaf beetle, Chrysomela scripta F. Larvae imbibed a droplet of B. thuringiensis var. san diego containing endotoxin and live spores. Sections of midgut were prepared for transmission electron microscopy at 15-min intervals during the first hour and then hourly for a duration of 3 hr. No signs of cellular disruption were observed until 2 hr after treatment. At this time midgut epithelial cells from treated larvae appeared more elongated and swollen than cells observed from control larvae, with the apical region of the cell bulging into the gut lumen. the cells contained large cytoplasmic spaces, expansion of the basal labyrinth, disruption of the rough endoplasmic reticulum, and apical displacement of the nuclei. No adverse effects were observed on microvilli, membranes, or organelles. after 3 hr cellular damage had increased, with cells ruptured at the apical surface and leakage of the cytoplasmic material into the gut lumen. B. thuringiensis var. san diego proliferated in the midgut lumen, producing additional endotoxin crystals during sporulation. Although cellular swelling caused by B. thuringiensis var. san diego endotoxin is similar to that reported for B. thuringiensis var. kurstaki endotoxin in lepidopterans, some differences were observed. These differences included lack of membrane lesion and mircrovillar damage and comparatively slow response.
KeywordsBacillus thuringiensis var. san diego; Chrysomela scripta; cottonwood leaf beetle; endotoxin; ultrastructure; midgut epithelium
Bauer, Leah S.; Pankratz, Stuart H. 1992. Ultrastructural Effects of Bacillus thuringiensis var. san diego on Midgut Cells of the Cottonwood Leaf Beetle1. Journal of Inverterbrate Pathology. Vol. 60 no. 1.:p. 15-25 (1992)