A toxic crystal protein encoded by a cry gene is obtained from which…

The correct answer is Option (4) → Bacillus thuringiensis

Some strains of the bacterium Bacillus thuringiensis (Bt) form protein crystals during a particular phase of their growth. These crystals contain a toxic insecticidal protein, and the genes that code for it are the cry genes. Bt cotton and other Bt crops carry these genes and so resist insects without the need for insecticides.

Option (1) E. coli — Incorrect. E. coli is the bacterium most used as a host in rDNA technology; it carries the vector pBR322 and was used to make insulin chains. It does not make the Bt crystal protein.

Option (2) Penicillium notatum — Incorrect. Penicillium notatum is the mould that gives penicillin, an antibiotic. It does not make an insecticidal protein.

Option (3) Streptococcus pneumoniae — Incorrect. Streptococcus pneumoniae is the bacterium used in Griffith’s transformation experiments, and it can cause pneumonia. It has no cry genes.

Option (4) Bacillus thuringiensis — Correct. Bacillus thuringiensis makes the crystal protein coded by the cry genes. The toxin kills insects such as lepidopterans, coleopterans and dipterans, which is why it is a bio-pesticide.

NCERT Extract:
Biotechnological Applications in Agriculture – “… 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.”
Biotechnological Applications in Agriculture – “… The choice of genes depends upon the crop and the targeted pest, as most Bt toxins are insect-group specific. The toxin is coded by a gene cryIAc named cry.”