Which one of the following is wrong statement ?

Options

A. Root nodule forming nitrogen fixers live as aerobes under free-living conditions
B. Phosphorus is a constituent of cell membranes, certain nucleic acids and all proteins
C. Nitrosomonas and Nitrobacter are chemoautrophs
D. Anamaena and Nostoc are capable of fixing nitrogen in free-living state also

Answer

To determine which statement is incorrect, let's analyze each option step by step:

### Step 1: Analyze Option A
- **Statement**: Root nodule forming nitrogen fixers live as aerobes under free living condition.
- **Analysis**: This statement is incorrect. Root nodule forming nitrogen fixers, such as Rhizobium, require anaerobic conditions to function effectively because the enzyme nitrogenase, which is responsible for nitrogen fixation, is inhibited by oxygen. Therefore, they do not thrive as aerobes in free-living conditions.

### Step 2: Analyze Option B
- **Statement**: Phosphorus is a constituent of cell membrane, certain nucleic acids, and all proteins.
- **Analysis**: This statement is correct. Phosphorus is indeed a component of phospholipids in cell membranes, is found in nucleic acids (as phosphate groups), and is also present in some proteins, particularly those that are phosphorylated.

### Step 3: Analyze Option C
- **Statement**: Nitrosomonas and Nitrovector are chemoautotrophs.
- **Analysis**: This statement is correct. Nitrosomonas and Nitrovector are bacteria involved in the nitrification process and are classified as chemoautotrophs because they obtain energy by oxidizing inorganic substances.

### Step 4: Analyze Option D
- **Statement**: Anabina and Nostoc are capable of fixing nitrogen in a free living state.
- **Analysis**: This statement is correct. Both Anabina and Nostoc are genera of cyanobacteria that can fix nitrogen independently in a free-living state.

### Conclusion
After analyzing all options, the incorrect statement is **Option A**.

### Final Answer
The wrong statement is: **Option A** - "Root nodule forming nitrogen fixers live as aerobes under free living condition."

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