What is true about Bt (Bacillus thuringiensis) strain ?

Question

Accepted Answer

Option 2 is correct: "The Bt-strains have been used for designing novel Bioinsecticidal plants."

Explanation:

1. **Justification for Option 2:**
   Bacillus thuringiensis (Bt) is a bacterium that produces proteins toxic to certain insects. These proteins, known as Bt toxins, are used in agriculture to control pest populations. Scientists have harnessed the genes responsible for producing these toxins and inserted them into the genomes of various crops, creating genetically modified organisms (GMOs) that can produce the Bt toxin themselves. This innovation has led to the development of bioinsecticidal plants, which are capable of defending themselves against specific insect pests, reducing the need for chemical pesticides and promoting sustainable agricultural practices.

2. **Explanation for why other options are incorrect:**

- **Option 1: "The concerned Bacillus has antitoxins."**
     This statement is incorrect because Bacillus thuringiensis does not produce antitoxins. Instead, it produces toxins that are harmful to certain insects. The term "antitoxins" would imply substances that neutralize toxins, which is not the function of Bt.

- **Option 3: "Bt-toxins exist as active toxins in the Bacillus."**
     This statement is misleading. Bt toxins are produced in an inactive form called protoxins within the bacterium. These protoxins become active only after being ingested by the insect and processed in its alkaline gut, where they are converted into active toxins that disrupt the insect's digestive system.

- **Option 4: "The activated toxins enter the ovaries of the pest to sterilize it and thus prevent its multiplication."**
     This statement is incorrect because Bt toxins do not function by entering the ovaries or sterilizing pests. Instead, they work by binding to receptors in the insect's gut, causing cell lysis and ultimately leading to the insect's death. The primary mode of action is not related to sterilization or affecting the reproductive system of the pest.

In conclusion, Option 2 is the correct answer because it accurately describes the application of Bt strains in developing bioinsecticidal plants, which is a significant advancement in agricultural biotechnology.