AIIMS 2006
- Exam
- AIIMS
- Year
- 2006
- Subject
- Botany
- Chapter
- Biological Classification
AIIMS 2006 · Botany · Biological Classification
Assertion : Gram-negative bacteria do not retain the stain when...
Assertion : Gram-negative bacteria do not retain the stain when washed with alcohol.
Reason : The outer face of the outer membrane of Gram-negative bacteria contains lipopolysaccharides, a part of which is integrated into the membrane lipids.
Options
- AIf both assertion and reason are true and reason is the correct explanation of the assertion
- BIf both assertion and reason are true but reason is not the correct explanation of the assertion
- CIf assertion is true, but reason is false
- DBoth assertion and reason are false statements.
Correct answer
A. If both assertion and reason are true and reason is the correct explanation of the assertion
Step-by-step solution
The technique of staining bacteria was given by a Dutch microbiologist Christian Gram (1884) and this technique is known as Gram staining. In the cell wall of gram +ve bacteria both horizontal and vertical peptide linkages are present due to which mesh is dense and stain does not come out. Futher outer layer of cell wall of Gram +ve bacteria is made up of techoic acid. In the cell wall of gram -ve bacteria, either horizontal or vertical peptide linkages are present, due to which mesh is loose and hence stain comes out when washed with alcohol. Further outermost layer of cell wall of Gram -ve bacteria is made up lipopolysaccharides.