Bioassay of solubilized Bacillus thuringiensis var. israelensis crystals by attachment to latex beads

Solubilized crystals of Bacillus thuringiensis var. israelensis were 7000 times less toxic to Aedes aegypti larvae than intact crystals, presumably because mosquito larvae are filter feeders and selectively concentrate particles while excluding water and soluble molecules. A procedure is described whereby soluble toxins are adsorbed to 0.8-micrometer latex beads, with retention of toxicity. The latex bead assay should make it possible to analyze the structure and mode of action of the mosquito toxin.