Read the following and answer questions from Q.1. to Q.5. given below:
Plants having foreign genes in their genome through genetic engineering are called transgenic plants. Genes can be incorporated either through a vector or through direct introduction of DNA. Bt cotton is a genetically modified organism which is pestresistant. It contains gene cry I Ac and cry II Ab of Bacillus thuringiensis. It is used to control lepidopterans, coleopterans and dipterans. Bt cotton can resist cotton bollworm and produce higher yields. Cry gene produces cry protein or Bt toxin. It is an endotoxin which remains as protoxin in plants and converted to active toxin after getting ingested by the insects. Alkaline pH of the insect gut solubilizes the protein crystals, the activated toxin creates pores to the mid guts wall of theinsects which cause them to death.
Bacillus thuringiensis is a

Options

A. air borne bacteria
B. soil borne fungus
C. soil borne bacteria
D. food borne bacteria

Explanation

**Step-by-step solution:**

1. **Understanding Transgenic Plants:**
- Transgenic plants are those that have been genetically modified to contain foreign genes. This is done through genetic engineering techniques.

2. **Introduction of Genes:**
- Genes can be introduced into plants either through vectors (like Agrobacterium tumefaciens) or by direct introduction of DNA into the plant cells.

3. **Example of a Transgenic Plant - Bt Cotton:**
- Bt cotton is a well-known example of a transgenic plant that has been modified to be pest-resistant. It contains specific genes from the bacterium Bacillus thuringiensis.

4. **Cry Genes:**
- The genes present in Bt cotton are cry I Ac and cry II Ab, which are responsible for producing a protein known as Bt toxin.

5. **Mechanism of Action:**
- The Bt toxin is an endotoxin that remains in an inactive form (protoxin) within the plant. When insects ingest it, the alkaline pH of their gut activates the toxin, leading to the formation of pores in the gut wall, which ultimately causes the death of the insect.

6. **Identifying Bacillus thuringiensis:**
- The question asks about the nature of Bacillus thuringiensis. It is important to recognize that it is a type of bacteria.

7. **Correct Answer:**
- Among the options provided (air-borne bacteria, soil-borne fungus, soil-borne bacteria, food-borne bacteria), the correct classification for Bacillus thuringiensis is **soil-borne bacteria**.

**Final Answer: C - Soil-borne bacteria.**

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