Parasporal Body of Bacillus thuringiensis israelensis

摘要: Since its discovery in Japan and Germany during the early part of this century, more than 25 subspecies spore-forming insecticidal bacterium Bacillus thuringiensis Berliner have been described (de Barjac 1985). The most distinctive characteristic is a parasporal body produced sporulation that consists primarily proteins (Angus 1965; Heimpel 1967; Aronson, Beckman, Dunn 1986; Hofte Whiteley 1989). In subspecies, bipyramidal crystal containing one or similar about 135 kDa are toxic to lepidopterous larvae. When ingested by larva, toxin-containing inclusion dissolves alkaline gut juices, midgut proteases cleave protoxin, yielding an active peptide toxin 60–70 kDa, δ-endotoxin. Although toxin’s precise mode action not fully understood, intoxication results osmotic imbalance across epithelial cell membrane, which leads quickly hypertrophy lysis cells. Lysis followed disruption basement leakage digestive juices into hemocoel, larval death (Luthy Ebersold 1981 ). δ-endotoxins different B. can vary considerably toxicity These variations thought be due differences amino acid sequence toxins, currently subject much interest because potential for increasing host spectrum through site-directed mutagenesis.