Why is it important to use fresh bacterial cells when performing a Gram stain?

• A. Fresh cells contain more DNA, which is necessary for the stain to work.
• B. Older cells may have damaged cell walls, leading to inaccurate Gram reaction results.
• C. Using fresh cells prevents contamination from environmental bacteria.
• D. Gram stain reagents only react with newly synthesized proteins in fresh cells.

Answer: (B)

Verified step by step guidance

1. Understand the principle behind the Gram stain: it differentiates bacteria based on the structure of their cell walls, specifically the thickness of the peptidoglycan layer.
2. Recognize that fresh bacterial cells have intact and well-preserved cell walls, which are essential for the crystal violet-iodine complex to be retained in Gram-positive bacteria.
3. Consider that older bacterial cells may undergo cell wall degradation or damage, which can cause the crystal violet stain to leak out, leading to false Gram-negative results even if the bacteria are Gram-positive.
4. Note that the Gram stain does not rely on DNA content or newly synthesized proteins, so these factors are not relevant to the accuracy of the staining process.
5. Conclude that using fresh cells ensures the structural integrity of the cell wall, providing reliable and accurate Gram stain results.