What is the expected color of a Bacillus subtilis smear after properly performing a Gram stain?
Understand the Problem
The question is asking about the expected color of Bacillus subtilis after a Gram stain procedure. Gram staining is a common technique in microbiology to differentiate bacterial species into two large groups (Gram-positive and Gram-negative) based on their cell wall constituents. Bacillus subtilis is a Gram-positive bacterium, meaning it has a thick peptidoglycan layer in its cell wall.
Answer
Purple
After a properly performed Gram stain, a Bacillus subtilis smear is expected to appear purple because Bacillus subtilis is a Gram-positive bacterium.
Answer for screen readers
After a properly performed Gram stain, a Bacillus subtilis smear is expected to appear purple because Bacillus subtilis is a Gram-positive bacterium.
More Information
Gram-positive bacteria have a thick peptidoglycan layer in their cell walls, which retains the crystal violet stain during the Gram staining procedure, resulting in a purple appearance under the microscope.
Tips
A common mistake is to confuse Gram-positive and Gram-negative bacteria. Gram-positive bacteria stain purple, while Gram-negative bacteria stain pink or red.
Sources
- Gram Staining - StatPearls - NCBI Bookshelf - ncbi.nlm.nih.gov
- GRAM STAIN – Laboratory Exercises in Microbiology - open.maricopa.edu
- Bacillus subtilis - Wikipedia - en.wikipedia.org
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