What is correct about Escherichia coli and Rhizobium japonicum ?

Options

A. E. coli Gram (-) and R. japonicun Gram (+)
B. Both Gram (+)
C. Both Gram (-)
D. E. coli Gram (+) and R. japonicun Gram (-)

Answer

To answer the question regarding Escherichia coli and Rhizobium japonicum, we will analyze the characteristics of both bacteria step by step.

### Step 1: Identify the Characteristics of Escherichia coli
- Escherichia coli (E. coli) is a rod-shaped bacterium.
- It is classified as a facultative anaerobe, meaning it can survive with or without oxygen.
- E. coli is primarily found in the intestines of humans and is known to be a commensal organism.

### Step 2: Identify the Characteristics of Rhizobium japonicum
- Rhizobium japonicum is also a rod-shaped bacterium.
- It is known for its ability to fix nitrogen, which is essential for plant growth.
- R. japonicum forms a symbiotic relationship with soybean plants (Glycine max).

### Step 3: Determine the Gram Staining Characteristics
- Both E. coli and R. japonicum are classified as gram-negative bacteria.
- Gram-negative bacteria have a thinner peptidoglycan layer and an outer membrane composed of lipopolysaccharides and lipoproteins.

### Step 4: Evaluate the Options Given
1. **E. coli is gram-negative and R. japonicum is gram-positive**: This is incorrect because R. japonicum is also gram-negative.
2. **Both are gram-positive**: This is incorrect as both are gram-negative.
3. **Both are gram-negative**: This is correct.
4. **E. coli is gram-positive and R. japonicum is gram-negative**: This is incorrect because E. coli is gram-negative.

### Conclusion
The correct statement about Escherichia coli and Rhizobium japonicum is that **both are gram-negative bacteria**.

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