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.

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