NEETZoologyBiotechnology and Its Applications
Bacillus thuringiensis forms protein crystals during a particular phase of its growth. These crystals contain a toxic insecticidal protein. Why does this toxin not kill the Bacillus itself?
Options
- AThe toxin exists in the bacterium as an inactive protoxin.
- BThe bacterium produces a specific antitoxin protein that neutralizes the toxic effect.
- CThe toxin is enclosed within specialized lysosomes inside the bacterial cell.
- DThe toxin is immediately excreted out of the bacterial cell upon synthesis.
Correct answer
A. The toxin exists in the bacterium as an inactive protoxin.
Step-by-step solution
Bacillus thuringiensis produces insecticidal proteins in the form of crystalline inclusions. These proteins do not kill the bacterium because they are synthesized in an inactive form called protoxin. The protoxin requires an alkaline pH to solubilize and become active, a condition that is present in the insect gut but not within the bacterial cell. The distractors are incorrect because bacteria lack lysosomes, the toxin is stored as intracellular crystals rather than being immediately excreted, and the survival is