A bacterium Bacillus thuringiensis produces a toxic protein named 'cry protein' that is lethal to certain insects but not to bacterium.
(a) Why this toxin does not kill bacteria?
(b) How man has exploited this protein for his benefit?

Dear student.
Please find the solution below.

a. Cry proteins are encoded by cry genes. These proteins are toxins, which are produced by Bacillus thuringiensis bacteria. This bacterium contains these proteins in their inactive from. So the protein does not kill bacteria. 

b.  When the inactive cry toxin protein is ingested by the insect, it gets activated by the alkaline pH of the gut. This results in the lysis of epithelial cell and eventually the death of the insect. Therefore, man has exploited this protein to develop certain transgenic crops with insect resistance such as Bt cotton, Bt corn, etc.



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