In Vitro Analyses of Bacillus thuringiensis δ-Endotoxin Action

Abstract

The purpose of the present report is to review the literature as it pertains to the mechanism of action of Bacillus thuringiensis (B.t.) endotoxins as determined by in vitro experimentation. As a means toward providing a focus to this report, we will only discuss those studies that employ lepidopteran-derived model systems and lepidopteran-specific B.t. endotoxins. The use of cell culture and isolated tissue preparations, which comprise the primary model systems for in vitro experimentation, has certain limitations. In most instances, the insect cells used in tissue culture are not considered the primary target for endotoxin interactions, ie. the columnar cells of the midgut epithelium. This is due to the fact that attempts at establishing a continuous line of insect derived midgut epithelial cells have not been successful. In like manner, the use of isolated target organ tissues like the midgut, or tissues or subfractions prepared therefrom, may destroy effective cellular