[Biochemical determination of B. thuringiensis thermostabile, exotoxin, using the inhibition of bacterial RNA polymerases].

This method can determine amounts of exotoxin near 1 mug. Used on the autoclaved filtrates of cultures of B. thuringiensis var. thuringiensis (serotype 1 type-strain), it shows an excretion rate of 250 to 300 mug per millilitre. The results on different exotoxin-producer strains give a perfect parallelism with the results obtained by bio-assays on Insects, but the biochemical method is more accurate and reproducible. This biochemical technique allows us, for the first time, to place the exotoxin excretion during the sporulation stage and not during the exponential growth.