Question

The Bt toxin produced by Bacillus thuringiensis does not harm the bacteria because

• A. the bacteria has proteins that neutralise the toxin
  
• B. the toxin is released in an inactive form within the bacteria
  
• C. the acidic nature of the bacterial cytoplasm destroys the toxin
  
• D. Both b and c
  

Answer 1

The correct option is B the toxin is released in an inactive form within the bacteria


Bacillus thuringiensis is a soil bacterium which is widely used as a biopesticide in the field of agriculture. Often, spores of B. thuringiensis are spread over crops to kill insect pests.
The cry genes, present in B. thuringiensis, code for a crystalline endotoxin protein or Cry protein, commonly known as Bt toxin. The toxin is released as an inactive protoxin within the bacteria and is activated at an alkaline pH.

Upon ingestion of the bacterial spores by the insects, the protoxin is released in their gut and the alkaline medium of the insect gut activates the protoxin.

The active toxin binds to the epithelial cells of the midgut of the insects and creates pores in the gut wall. The insect stops eating at this point and eventually dies due to starvation.