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. Anabaena and Nostoc are capable of fixing nitrogen in free-living state also

Answer

To determine which statement is wrong, we will analyze each of the four statements provided in the question.

### Step-by-Step Solution:

1. **Analyze the First Statement:**
- Statement: "Root nodule forming nitrogen fixer live as aerobes under free living condition."
- Explanation: Nitrogen-fixing bacteria, such as Rhizobium, form symbiotic relationships with the roots of leguminous plants. These bacteria can exist as aerobes in the soil, which is true. Therefore, this statement is **correct**.

2. **Analyze the Second Statement:**
- Statement: "Phosphorus is a constituent of cell membranes, certain nucleic acids, and all proteins."
- Explanation: Phosphorus is indeed a component of cell membranes (in the form of phospholipids) and is a crucial part of nucleic acids (DNA and RNA). However, it is not a constituent of all proteins; it is present in only certain proteins. Therefore, this statement is **incorrect**.

3. **Analyze the Third Statement:**
- Statement: "Nitrosomonas and Nitrobacter are chemoautotrophs."
- Explanation: Nitrosomonas and Nitrobacter are nitrifying bacteria that obtain energy by oxidizing inorganic nitrogen compounds. This characteristic classifies them as chemoautotrophs. Therefore, this statement is **correct**.

4. **Analyze the Fourth Statement:**
- Statement: "Anabina and Nostoc are capable of fixing nitrogen in free living state."
- Explanation: Anabina and Nostoc are types of blue-green algae (cyanobacteria) that can fix atmospheric nitrogen due to the presence of specialized cells called heterocysts. This statement is also **correct**.

### Conclusion:
The wrong statement among the four provided is the **second statement**: "Phosphorus is a constituent of cell membranes, certain nucleic acids, and all proteins."

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