EFFECT OF NEMATOCIDAL BACILLUS-THURINGIENSIS STRAINS ON FREE-LIVING NEMATODES .2. ULTRASTRUCTURAL ANALYSIS OF THE INTOXICATION PROCESS IN CAENORHABDITIS-ELEGANS

Transmission electron microscopy is used to describe the intoxication in Caenorhabditis elegans, feeding on toxic spore/crystals of Bacillus thuringiensis. The toxin acts directly against the intestine, first b y affecting the anteriormost ring of four intestinal cells. Over a per iod of 12 hours, these cells lose much of their volume, the microvilli regress slowly, several cell organelles undergo dramatic change and a re ultimately destroyed. No rupture of the apical intestinal cell memb rane is observed. Non-intestinal tissues seem unaffected. This study i ndicates considerable ultrastructural differences in the mode of actio n between the nematicidal toxin and the insecticidal crystal toxins fr om B. thuringiensis.