Bacterium responsible for the curdling of milk is

Options

A. Lactobacillus
B. E. coli
C. Rhizobium
D. Plasmodium.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the bacterium responsible for the curdling of milk. This indicates we need to identify a specific type of bacteria involved in the process of converting milk into curd.

2. **Identifying the Options**: The options provided are Lactobacillus, E.coli, Rhizobium, and Plasmodium. We need to analyze each of these to determine which one is involved in curdling milk.

3. **Analyzing Lactobacillus**: Lactobacillus is a type of lactic acid bacteria that is known for its role in fermenting milk. It converts lactose (the sugar in milk) into lactic acid, which leads to the coagulation of milk proteins, resulting in curd formation.

4. **Examining E.coli**: Escherichia coli (E.coli) is primarily known for its role in the intestines and is not involved in the curdling of milk. It is more associated with foodborne illnesses.

5. **Considering Rhizobium**: Rhizobium is a nitrogen-fixing bacterium that forms symbiotic relationships with legumes. It does not play a role in milk fermentation or curdling.

6. **Looking at Plasmodium**: Plasmodium is not a bacterium; it is a protozoan responsible for causing malaria in humans. Therefore, it is irrelevant to the question.

7. **Conclusion**: Based on the analysis, Lactobacillus is the correct answer as it is the bacterium responsible for the curdling of milk.

**Final Answer**: The bacterium responsible for the curdling of milk is **Lactobacillus**.

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