The nitrogen - fixing bacteria Rhizobium is ……….... in nature.

Options

A. chemoautotrophic
B. photoautotrophic
C. chemosynthetic
D. heterotrophic

Answer

To solve the question regarding the nature of the nitrogen-fixing bacteria Rhizobium, we can follow these steps:

### Step 1: Understand Nitrogen Fixation
Nitrogen fixation is the process by which atmospheric nitrogen (N₂) is converted into ammonia (NH₃), which can then be utilized by plants. This is crucial because plants cannot directly use atmospheric nitrogen.

**Hint:** Remember that nitrogen fixation is essential for converting unusable nitrogen into a form that plants can absorb.

### Step 2: Identify the Type of Bacteria
Rhizobium is a type of nitrogen-fixing bacteria that forms a symbiotic relationship with leguminous plants. This means it lives in close association with these plants and aids them in nitrogen fixation.

**Hint:** Focus on the relationship between Rhizobium and legumes to understand its ecological role.

### Step 3: Classify Rhizobium's Nutritional Mode
We need to determine the nutritional mode of Rhizobium from the options provided:
- Chemoautotrophic
- Photoautotrophic
- Chemosynthetic
- Heterotrophic

Rhizobium is classified as **chemoautotrophic** because it derives its energy from the oxidation of inorganic compounds rather than sunlight or organic compounds.

**Hint:** Chemoautotrophs obtain energy from chemical reactions involving inorganic substances.

### Step 4: Confirm the Correct Answer
Given the classification of Rhizobium as a nitrogen-fixing bacterium that does not rely on sunlight for energy, we conclude that the correct answer is **chemoautotrophic**.

**Hint:** Review the definitions of the other options to ensure clarity on why they do not apply to Rhizobium.

### Final Answer:
The nitrogen-fixing bacteria Rhizobium is **chemoautotrophic** in nature.