To study toxicity of 76 laboratory‐grown strains of planktonic cyanobacteria to mosquito larvae, hydrophilic and lipophilic cell‐free extracts of cyanobacteria were incubated with larvae of the Aedes aegypti mosquito and death percentages were followed during 2 days. Toxicity was clearly associated with hepato ‐ and neurotoxins of the samples. A strain of Microcystis aeruginosa was most effective, and caused death of the larvae due to a single hepatotoxin. Pure mammalian neurotoxin, anatoxin‐a, was also toxic, and probably acted as a neurotoxin with the mosquito larvae.
SummaryThe exotoxin produced by certain serotypes of Bacillus thuringiensis was used as a means of microbiological control of the larval development of flies. The optimal batch cultivation conditions with respect to pH, temperature, aeration, agitation, and initial concentration of growth-limiting substrate were determined. A dynamic model describing the process was designed and fitted to the experimental data. The application of a method for estimating exotoxin and bacterial concentrations from on-line measurable quantities such as oxygen consumption and heat production is presented.
Several medium ingredients locally available in Egypt were investigated for their ability to support δ-endotoxin production by two mosquito-toxic strains ofBacillus thuringiensis H-14 usingCulex pipiens for the bioassay of δ-endotoxin. Soya beans, black-eyed beans, common peas and lentils supported good production of toxin whereas peanuts, fodder yeast, cheese whey and corn steep liquor gave only low amounts of toxin. Molasses as the sole carbon source at 2 and 3% (w/v) with soya (or Proflo) as the sole nitrogen source at 3% gave the best yields of toxin for strain M1 and S128 respectively.
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