Bt Toxin (Bacillus thuringiensis Insecticidal Protein)

Soil bacterium Bacillus thuringiensis produces a crystal protein (Cry toxin) as a natural competitive/defensive trait, lethal to specific insect larvae that ingest it but harmless to most other organisms -- first isolated as a commercial insecticidal agent in the early 20th century (Ishiwata, 1901; not independently re-verified for this node). Vaeck, Reynaerts, Hofte, Jansens, De Beuckeleer, Dean, Zabeau, Van Montagu & Leemans (Plant Genetic Systems, Ghent), "Transgenic plants protected from insect attack" (Nature 328, 33-37, 1987-07-01, OpenAlex W2062706925, 922 citations) demonstrated the first transgenic crop plants expressing a cloned Bt toxin gene, the landmark that directly founded the commercial Bt-crop industry. This node anchors that translation event, not the original 1901 bacterial isolation.