Question

Given below are two statements, one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A): Gram negative bacteria do not retain the primary stain when washed with alcohol and subsequently stained again with secondary stain.
Reason (R): The outer membrane of gram negative bacteria contains lipopolysaccharides.
In light of the above statements, choose the correct answer from the options given below

• A. Both (A) and (R) are correct and (R) is the correct explanation of (A)
• B. Both (A) and (R) are correct but (R) is NOT the correct explanation of (A)
• C. (A) is correct but (R) is not correct
• D. (A) is not correct but (R) is correct

Answer 1

The Correct Option is A

To solve this question, we must analyze both the assertion and the reason provided and determine if the reason correctly explains the assertion.

1. Understanding the Assertion (A): "Gram negative bacteria do not retain the primary stain when washed with alcohol and subsequently stained again with secondary stain."
   • This statement is related to the Gram staining technique, which is a differential staining approach used to classify bacteria.
   • Gram negative bacteria are characterized by their inability to retain the crystal violet primary stain after being washed with alcohol. Instead, they take up the secondary (counter) stain, which is typically safranin, and appear red or pink.
2. Understanding the Reason (R): "The outer membrane of gram negative bacteria contains lipopolysaccharides."
   • Gram negative bacteria have a distinctive cell wall structure that includes an outer membrane composed of lipopolysaccharides (LPS), which contributes to their unique staining properties.
   • This outer membrane is unique to Gram negative bacteria and is absent in Gram positive bacteria.
3. Evaluating the Relationship: We need to determine if (R) correctly explains why Gram negative bacteria do not retain the primary stain.
   • The presence of the outer membrane with lipopolysaccharides is indeed the reason why the alcohol wash is effective at removing the crystal violet stain in Gram negative bacteria. The outer membrane is disrupted by alcohol, allowing the dye to be washed away.
   • Subsequently, these bacteria can take up the secondary stain due to their thinner peptidoglycan layer and disrupted outer membrane.

Based on the above analyses, both statements (A) and (R) are correct, and (R) is the correct explanation for why Gram negative bacteria behave in the described manner. Therefore, the correct answer is: Both (A) and (R) are correct and (R) is the correct explanation of (A).