G. Borgonie et al., EFFECT OF A NEMATOCIDAL BACILLUS-THURINGIENSIS STRAIN ON FREE-LIVING NEMATODES .3. CHARACTERIZATION OF THE INTOXICATION PROCESS, Fundamental and applied nematology, 19(6), 1996, pp. 523-528
The toxicity of Bacillus thuringiensis is temperature sensitive. Incub
ation of Caenorhabditis elegans with nematicidal B. thuringiensis stra
ins at 16, 20, and 25 degrees C shows that toxicity decreases as tempe
rature declines. At 16 degrees C, toxicity is completely lost, while i
t is maximal at 25 degrees C. Toxicity is pH sensitive and is signific
antly reduced when nematodes are incubated with the weak bases NH4Cl,
chloroquine, acridine orange, methyl red, and neutral red. Based on th
ese results, we proposed the hypothesis that the nematicidal factor is
effectively internalized into the intestinal cells, a sharp deviation
from the insecticidal B. thuringiensis toxins acting at the level of
the brush border membrane. Although the absence of purified toxin prev
ents a more definitive elucidation of the mode of action, the results
of this third and final part of this series of publications convincing
ly indicate that nematicidal B. thuringiensis do not hold the same pro
mise as a biological control agent as the insecticidal B. thuringiensi
s strains.