Name the source organism for Bt toxin. Why does Bt toxin not kill the bacterium that produces it but kill the insect that ingest it.
Answers
Answer:
Bt toxin is produced by bacteria Bacillus thuriengiensis. During sporulation, these bacteria forms intracellular crystalline bodies that contain an insecticidal protein called the endotoxin. Bt toxin does not kill the bacterium that produces it, but kill the insect that ingests it because the endotoxin that accumulates in the bacterium is an inactive precursor. It gets activated only in the alkaline gut of insect. When insect ingests it, then protoxin is cleaved by proteases (alkaline conditions in gut), resulting is shorter versions of the protein that display the toxic activity, by binding to the inside of the insects mid gut and damages the surface epithelium by creating pores that cause swelling and lysis. So, that insect is unable to feed and consequently starves to death
Explanation:
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Answer:
Some strains of Bacillus thuringiensis produce proteins that kill certain insects such as lepidopterans (tobacco budworm, armyworm) coleopterans (beetles) and dipterans (flies, mosquitoes).
B. thuringiensis forms protein crystals during a particular phase of their growth.
These crystals contain a toxic insecticidal protein.
The Bt toxin protein exists as inactive protoxins but once an insect ingests the inactive toxin, it is converted into an active form of toxin due to the alkaline pH of the gut which solubilise the crystals.
The activated toxin binds to the surface of midgut epithelial cells and create pores that cause cell swelling and lysis and eventually cause death of the insect.