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Bacillus thuringiensis insecticidal delta‐endotoxin: Diversity of crystal proteins and its relatedness to the toxicity spectrum
Author(s) -
Haider M. Z.,
Mahmood S.
Publication year - 1990
Publication title -
journal of basic microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.58
H-Index - 54
eISSN - 1521-4028
pISSN - 0233-111X
DOI - 10.1002/jobm.3620300406
Subject(s) - bacillus thuringiensis , antiserum , biology , molecular mass , microbiology and biotechnology , toxin , biochemistry , bacteria , antigen , enzyme , genetics
Bacillus thuringiensis strains produce crystal delta‐endotoxins which exhibit a diverse toxicity spectrum. In order to explore the basis of toxin specificity, a comparison of the activity of 13 strains belonging to seven serotypes was made against three insect species. The delta‐endotoxin crystals were purified and their poly‐peptide composition analyzed by SDS‐PAGE. Among the strains studied, the delta‐endotoxins consist of a variety of crystal proteins in the 60‐144 KDa size range. On the basis of molecular mass, endotoxins maybe grouped into two classes; one contained both high (125‐144 KDa, P1) and medium sized (60–66 KDa, P2) proteins and a second class consisting of only the high M r polypeptides. Immunoblotting with B. alzawai P1 antiserum revealed antigenic cross‐reaction with one or more of the polypeptides in 125‐144 KDa range in all the strains studied. When the crystal proteins from different strains were immunoblotted with kurstaki P2 antiserum, none of the P1 protein crossreacted suggesting that the P1 and P2 proteins are not structurally related. However, the B. kurstaki P2 antiserum crossreacted with 66 KDa proteins in some other strains which underlines a structural homology in this class of the toxic polypeptides. Toxicity studies revealed that the high M r P1 proteins of all the strains in this study were active against lepidopteran ( Pieris brassicae and Diacrisia obliqua ) larvae. B. thuringiensis aizawai strains exhibit a dual toxicity associated with the high M r (130–135 KDa; P1) proteins. The P2 crystal proteins (60–66 KDa) also showed dual toxicity against the lepidopteran and dipteran larvae but were found to be structurally and immunologically distinct.