Bacteria which retain purple colour after staining with Gram stain is

Options

A. Gram +ve
B. Gram - ve
C. Trichous
D. Spirillum.

Answer

**Step-by-Step Solution:**

1. **Understanding Gram Staining:** The Gram staining technique is a method used to classify bacteria into two main groups based on their cell wall composition. This technique involves applying a series of stains to the bacteria.

2. **Identifying Gram Positive Bacteria:** Bacteria that retain the purple color after the Gram stain procedure are classified as Gram positive. This is because they have a thick peptidoglycan layer in their cell wall that retains the crystal violet stain used in the process.

3. **Identifying Gram Negative Bacteria:** In contrast, Gram negative bacteria do not retain the purple color. They have a thinner peptidoglycan layer and an outer membrane that allows the crystal violet stain to be washed out during the decolorization step with alcohol. Instead, they take up a counterstain (usually safranin) and appear pink.

4. **Conclusion:** Based on the information provided, the bacteria that retain the purple color after Gram staining are classified as Gram positive bacteria.

**Final Answer:** The bacteria which retain purple color after staining with Gram stain is **Gram positive**.

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