Question

Bacillus thuringiensis forms protein crystals which contain insecticidal protein, that

• A. Binds with epithelial cells of midgut of the insect pest ultimately killing it.
• B. Is coded by several genes including the gene cry.
• C. Is activated by acid pH of the foregut of the insect pest.
• D. Both A and B

Answer 1

Answer: (D)

Both A and B

Bacillus thuringiensis forms crystals, proteinaceous insecticidal delta-endotoxins, called as crystal proteins or Cry proteins, which are encoded by cry genes. In most strains of Bacillus thuringiensis, the cry genes are located on a plasmid. It serves as an important reservoir of Cry toxins. When insects ingest toxin crystals, their alkaline digestive tracts denature the insoluble crystals, making them soluble and thus amenable to being found in the insect gut, which liberates the toxin from the crystal. The Cry toxin is then inserted into the insect gut cell membrane, paralysing the digestive tract and forming a pore. The insect stops eating and starves to death.
Therefore, the correct answer is option D.