What color do Gram negative bacteria appear after a Gram stain?
Understand the Problem
The question is asking about the appearance of Gram negative bacteria after performing a Gram stain, which is a common microbiological technique used to differentiate bacterial species based on their cell wall structure.
Answer
Pink to red.
Gram-negative bacteria appear pink to red after a Gram stain.
Answer for screen readers
Gram-negative bacteria appear pink to red after a Gram stain.
More Information
Gram-negative bacteria appear pink to red due to their thin peptidoglycan layer allowing the crystal violet stain to wash out, leaving them to take up the counterstain, usually safranin or fuchsine.
Tips
A common mistake is confusing the coloration with Gram-positive bacteria, which appear purple to blue. Verify staining by considering the bacteria cell wall structure.
Sources
- Gram Staining - StatPearls - NCBI Bookshelf - ncbi.nlm.nih.gov
- Gram Stain Protocols - American Society for Microbiology - asm.org
- Gram-positive and gram-negative: What is the difference? - medicalnewstoday.com
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