| Sumario: | This study was carried out to determine the persistence of toxicity of fermentation extracts of Bacillus thuringiensis var. israelensis
after more than three decades of storage. For this purpose, a population of Aedes aegypti was established. The mortality rate of
20 spore-crystal extracts purified using the acetone-lactose coprecipitation method was measured and evaluated by bioassays
according to a modified WHO protocol. The extracts with the highest mortality rate were determined in triplicate by their LD50
and LD98. All extracts showed toxicity at the highest tested dose (1000 ppm) and some, such as strains 3260 and 3501, still killed
larvae at doses as low as 0.01 ppm. These data are surprising because no study on the activity of B. thuringiensis toxic proteins after
such a long storage time has been reported.
|
|---|
