Activity against toxins

A possible example of this thesis is the crystalline insect toxin found in Bacillus thuringiensis spores and discussed here by Dr. Anderson. Although neither the bacillus nor its spores exhibit useful antibiotic activity against other microorganisms, the very specific toxicity to insects has become of major commercial interest. The enormous number and variety of fungal species available for further examination must lead inevitably to one or more which produces pesticidal metabolites. 

Materials produced by crystalliferous bacilli which elicit a toxic response in susceptible insects may be separated into two types. The first type, the true toxins, include the crystalline protein inclusion body the parasporal body of Hannay (14)], a heat-stable, water-soluble exotoxin active against flies, a heat-stable, dialyzable water-soluble exotoxin, toxic to Lepidoptera on injection (23), and a heat-labile, water-soluble, filterable exotoxin, toxic toward larch sawfly larvae (Hymenoptera) which was reported by Smirnoff (31). 

Fig. 17. The STARFISH dodecamer of Kitov et al. with the Pk trisaccharide linked laterally at 2 and showing subnanomolar inhibitory activity against Shiga-like toxin I.23... 

Different subspecies have been shown to be active against different orders of insect. Although the method of insect death is the same, the different endotoxins either have different binding regimes or are activated by the gut enzymes of different insect species and this leads to the differences in activity spectrum. There is evidence, however, that different insect orders act upon the delta-endotoxins in different ways. Treatment of a pro-toxin with lepidopteran gut juice leads to a toxin that is active against Lepidoptera whereas treatment with dipteran gut juice produces... 

Following the first report of tumor promotion by okadaic acid, additional tumor promoters of the okadaic acid activity class have been identified, e.g., microcystin [513,514], and calyculin derivatives, Fig. (63) reported in marine sponges such as Discodermia calyx [515] and Theonella swinhoei [516] as potent inhibitors of tumor cell proliferation. A two-sponge association, Poecillastra sp. and Jaspis sp., yielded cytotoxic toxins which exhibited selective activity against several tumoral cell lines [517],... 

Bacillus thuringiensis Berliner (commonly known as Bt) is an insecticidal bacterium discovered in the early 20th century. The commercial Bt products are powders containing a mixture of dried spores and crystalline 8-endotoxin, but some contain only the toxin component. Both spores and toxin crystals are produced within the bacterial vegetative cell by Bt (Figure 4.12). Currently, there are six strains that possess specific activity against different insect species as follows ... 

Honkanen, R.E., Codispoti, B.A., Tse, K., Boynton, A.L., and Honkanan, R.E. 1994. Characterization of natural toxins with inhibitory activity against serine/threonine protein phospatases. Toxicon 32(3) 339-350. 

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