Q.(a) Give the scientific name of the bacteria widely used in biotechnology to create a GM cotton crop resistant to bollworm attacks.
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Start your 14-day free trial to unlock the full solution →Bacillus thuringiensis produces Bt toxin that exists as an inactive protoxin in the bacterium but becomes lethal to bollworms when activated in the insect's alkaline gut; GM cotton carries the toxin gene, making the plant itself produce this insect-specific poison.
The Bacterium Behind Bt Cotton
The scientific name of the bacterium is Bacillus thuringiensis, often abbreviated simply as Bt. This soil-dwelling microbe has been a gift to agricultural biotechnology because it naturally produces a protein toxic to certain insects but harmless to humans, other mammals, and most beneficial insects. The discovery that its genes could be transferred into cotton plants revolutionized pest management, particularly against the cotton bollworm (Helicoverpa armigera), one of the most destructive pests in Indian agriculture.
Why Bt Toxin is Inactive in the Bacterium
Here's the elegant part of the story: Bacillus thuringiensis produces the toxin as an inactive protoxin (also called a crystal protein or Cry protein, because it forms crystalline inclusions inside the bacterial cell). The bacterium itself is not harmed because the toxin remains in this dormant, non-toxic form. Think of it as a weapon kept safely locked—dangerous only when the right key turns.
The protoxin needs specific conditions to become active, conditions that exist in the target insect but not in the bacterium. This is a survival strategy: the bacterium can manufacture a potent insecticide without poisoning itself.
How the Toxin Becomes Lethal in the Insect
When a bollworm larva feeds on a Bt cotton plant, it ingests the Bt protoxin crystals along with the plant tissue. The insect's gut provides exactly the environment needed to unlock the toxin:
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Alkaline pH: The bollworm's midgut is highly alkaline (pH around 9–10), unlike the neutral or slightly acidic conditions in the bacterial cell. This alkaline environment is the first trigger.
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Protease enzymes: The insect's digestive system contains specific protease enzymes that cleave the inactive protoxin, converting it into its active toxic form.
Once activated, the toxin binds to specific receptor sites on the epithelial cells lining the insect's midgut. This binding creates pores in the cell membranes, disrupting the gut lining. The insect stops feeding, its gut is paralyzed, and it eventually dies—usually within a few days. …
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