A new class of Bacillus thuringiensis delta-endotoxins, or insecticidal control proteins (ICPs), is defined by an apparently cryptic protein with a unique primary structure and novel entomocidal specificity for certain coleopteran and lepidopteran species. The discovery of a new group of ICPs will extend the use of this natural insecticide in integrated pest-management systems.

Deletion mutagenesis analysis of a duplicated gene necessary for Haemophilus influenzae serotype b capsule expression showed that only one functional copy of this gene is required for capsule production and for virulence in infant rats. Mutant strains generated in this study differed from each other and from the parental strain in their ability to maintain the large tandem duplication which contains the genes involved in serotype b capsule expression.

Two C-terminal deletion constructs were made to study the effect of such deletions on the biological activity of the CryV protein of Bacillus thuringiensis subsp. kurstaki. The results of feeding on neonatal larvae of Ostrinia nubilalis (European corn borer [ECB]) indicated that the 50% lethal dose of the full-length CryV protein was 3.34 g/g of diet (95% fiducial limits, 2.53 to 4.32 g/g of diet). Removal of 71 amino acids (aa) from the C terminus had little effect on toxicity, whereas deletion of 184 aa abolished the insecticidal activity of the CryV protein completely. Truncations of the full-length CryV protein were also generated with trypsin and the midgut protease of ECB. The proteolytically treated products were characterized by determining their Nterminal amino acid sequences. The CryV protein was found to be cleaved by both proteases through a two-step process. Initially an intermediary form was generated which contained aa 45 of full-length CryV as its N-terminal end. The C-terminal end of this peptide was not experimentally determined. However, analysis of the deduced amino acid sequence of CryV indicated that the C-terminal end of the intermediary form is likely either aa 655 or 659. Further N-terminal processing of the intermediary form resulted in a protease-resistant core form. The core included aa 156 to aa 655 or 659. While the intermediary form retained 100% of the ECB larval toxicity, the core form exhibited only ϳ22% of the toxicity of the full-length protein.

Within the region of the Haemophilus influenzae serotype b genome required for capsule expression, a 4.6-kilobase segment was cloned, used as a hybridization probe, and found to be specific for serotype b strains. Deletion mutagenesis within this segment defined a locus necessary for serotype b capsule production and another involved in maintenance of wild-type colony appearance.