Question

Which of the following stain/s is used by Hans Christian Gram to classify bacteria as gram-negative and gram-positive bacteria?
a. Carbolfuchsin
b. Safranin
c. Crystal violet
d. All of the above

Answer 1

Hint: Gram staining is a different type of staining to differentiating between bacteria.

Complete answer:
Bacteria are microscopic, single-celled organisms that thrive in diverse environments. These organisms can live in soil, the ocean and inside the human gut.

1. Bacteria are classified as gram-positive and gram-negative bacteria.
2. Crystal violet is the primary stain used first then after washing with alcohol counterstain is added.
3. Bacteria which will get stain appear purple violet in colour under a microscope are gram-positive.
4. Gram-positive organisms' cell wall contains higher lipid content so the primary stain does not wash away.
5. Carbolfuchsin is a phenolic compound used to stain bacteria because it is lipid-soluble and penetrates the waxy cell wall.
6. Safranin stain is used as counterstain gram-negative bacteria will lose: the primary stain and gets stained by safranin (pink).

So, the correct answer is 'all of the above'.

Note: Gram-negative bacteria – E.coli, Pseudomonas, Klebsiella pneumoniae, Neisseria, etc. Gram-positive bacteria-Staphylococcus, Streptococcus, Mycobacterium, Clostridium etc.