DENNIS KUNKEL MICROSCOPY / SCIENCE PHOTO LIBRARY DENNIS KUNKEL MICROSCOPY / SCIENCE PHOTO LIBRARY
Coloured scanning electron micrograph (SEM) of Bacillus thuringiensis. Gram-positive, spore forming, soil bacterium (prokaryote). Bacillus thuringiensis produces a toxin called Cry toxin. The bacterium itself can be used as a biological control agent or the isolated toxin can be used as a commercial insecticide. B. thuringiensis was first used in Germany in 1911 as a bacterial pathogen for flour moths. Spraying or dusting plants with spores of this bacterium appear to be an environmentally safe way to attack such pests as the gypsy moth, the tent caterpillar, and the tobacco hornworm. B. thuringiensis is considered safe to humans. The bacteria kill larvae when they ingest the bacterium and thus the toxin they produce. Other strains of B. thuringiensis have been developed to control specific insects, such as mosquitoes and potato beetles. Magnification: x4,000 when shortest axis printed at 25 millimetres.
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