Paul G. Fast

Bacillus thuringiensis crystal toxin: Ultrastructural studies of its effect on silkworm midgut cells

Abstract Bacillus thuringiensis crystal toxin induced a cytoplasmic response in columnar cells within 1 min after ingestion although external symptoms were not exhibited by larvae until 15 min after ingestion. Microvilli became less consistently uniform in diameter; their organized internal microfilaments were disrupted and disappeared. The cisternae of rough endoplasmic reticulum were enlarged and denuded of ribosomes. By 5 min after ingestion, microvilli of some columnar cells disappeared entirely and gross ultrastructural changes were observed in other regions of the cells. Up to 5 min after ingestion there were few, if any, ultrastructural changes observed within goblet cells. Mitochondria in columnar cells were swollen but did not exhibit the condensed configuration reported by other workers. Both the buffer system used in the fixation medium and its osmolarity influenced the changes in the ultrastructure of midgut cells exposed to B. thuringiensis crystal toxin.

Occurrence of two serologically distinct groups within Bacillus thuringiensis serotype 3 ab var. kurstaki.

Abstract Two groups distinguishable on the basis of crystal serology have been identified within Bacillus thuringiensis var kurstaki (serotype 3 ab). The toxicities of these two groups to Trichoplusia ni and Heliothis virescens expressed as T H ratio also differed. It is suggested that serotype 3 ab be separated into two subgroups designated as K-1 and K-73.

The δ-endotoxin of Bacillus thuringiensis: V. On the occurrence of endotoxin fragments in hemolymph☆

Abstract Leucine- 3 H labeled crystals of Bacillus thuringiensis δ-endotoxin were fed to last-instar larvae of spruce budworm, Choristoneura fumiferana , eastern forest tent caterpillar, Malacosoma disstria , and silkworm, Bombyx mori . Radioactivity was detected in hemolymph 1 min after feeding in the first two species, but not until 3–5 min after feeding in silkworm larvae. Most of the radioactivity from hemolymph of all three species eluted from gel filtration columns at the same elution volume indicating similar moleculear weights (