Question

The component of bacteria that retains the crystal violet stain during Gram-staining is-
a) O-antigen
b) Lipopolysaccharide
c) Peptidoglycan
d) Cytoplasmic membrane

Answer 1

Hint: Gram staining is a common technique used for differentiating different groups of bacteria on the basis of the cell wall component. It is a differential stain. The two groups are differentiated as gram positive or gram negative by staining the cells red or violet.

Complete answer:
To solve this question, we must know about the gram staining technique and the difference between gram positive and negative bacteria.
Gram staining technique- The staining of any sample is done by following the basic steps-
The primary stain crystal violet is applied and heat fixed.
Gram iodine called the moderant is applied.
Decolourisation by the help of alcohol.’
Counterstaining with safranin.
Result- The bacteria which retains the crystal violet colour is called gram positive. It is because of the thick layer of peptidoglycan in their cell wall. The gram negative has a thin layer of peptidoglycan but a thick layer of lipid. The peptidoglycan layer retains the colour of the crystal violet.
O-Antigen and lipopolysaccharide are present in the outer membrane of gram-negative bacteria. This layer is stained red as it cannot retain crystal violet after washing with alcohol.
Cytoplasmic membrane or the cell membrane is similar in both kinds of bacteria.

So, the correct answer is option C.

Note:
Decolourising or washing with alcohol or acetone is the most important step in the gram staining.
Gram staining differentiates a wide range of pathogens. Quick identification of the pathogens can be made and antibiotics can be prescribed significantly.
Gram positive bacteria are more resistant to antibiotics due to the thick peptidoglycan layer.