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The toxicity of Bacillus thuringiensis and B. sphaericus, insecticidal bacteria that have been used widely for insect pest and vector control, is due to insecticidal protein crystals produced during sporulation. Whereas the insecticidal crystals of these two species have been studied extensively owing to their practical value, there are several other lesser known entomopathogenic bacteria that also produce either crystalline or noncrystalline protein inclusions, some of which are insecticidal. For example, Paenibacillus popilliae, a biological control agent of grubs, the immature stages of beetle larvae, forms parasporal crystals toxic to scarab larvae. A mosquitocidal strain of Clostridium bifermentans produces parasporal inclusion bodies lacking a crystalline structure. Mosquitocidal strains of Brevibacillus laterosporus produce crystalline inclusions of various shapes and sizes. In addition, two nematode-symbiotic bacteria, Photorhabdus luminescens and Xenorhabdus nematophilus produce large amounts of crystalline proteins that are not toxic to insects. In this paper, the characteristics of the protein inclusions produced by these entomopathogenic bacteria are described. |
