In which bacteria lipopolysaccharide is found as the main surface antigen

Options

A. Gram negative bacteria
B. Gram positive bacteria
C. Cyonobacteria
D. All the above.

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks which type of bacteria has lipopolysaccharide (LPS) as the main surface antigen.

2. **Definition of Antigen**: An antigen is a substance that induces an immune response in the body. It can be a part of pathogens like bacteria.

3. **Identifying Types of Bacteria**: The options provided are:
- Gram-negative bacteria
- Gram-positive bacteria
- Cyanobacteria
- All of the above

4. **Lipopolysaccharide (LPS)**: It is important to note that lipopolysaccharides are primarily found in the outer membrane of Gram-negative bacteria. They play a critical role in the immune response as they can act as antigens.

5. **Analyzing the Options**:
- **Gram-negative bacteria**: They contain lipopolysaccharides in their cell wall structure. This makes them a suitable candidate.
- **Gram-positive bacteria**: They have a different cell wall structure that does not include lipopolysaccharides.
- **Cyanobacteria**: These are photosynthetic bacteria (often referred to as blue-green algae) and do not contain lipopolysaccharides in the same way Gram-negative bacteria do.
- **All of the above**: This option is incorrect as only Gram-negative bacteria contain lipopolysaccharides.

6. **Conclusion**: Based on the analysis, the correct answer is that lipopolysaccharide is found as the main surface antigen in **Gram-negative bacteria**.

**Final Answer**: Gram-negative bacteria

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