Gentian violet colouration of gram positive bacteria is due to -

Ans. is 'a' i.e., Peptidoglycan GRAM STAININGo The gram stain differentiates bacteria into two broad groups1. Gram positive - Resist decolourization and retain primary stain, appear violet.2. Gram negative - Decolourised by organic solvents, and therefore, take the counterstain, appearing red.Smear stained with gentian violet (primary stain)|Application of dilute solution of iodine|Decolourisation with organic solvent, e.g., ethanol|Counterstaining by carbol fuchsin|||Retain primary stain (violet)|Gram positiveTake colour of counterstain (red)|Gram negativeWhy do gram-positive organisms retain primary stain, but not gram negative organisms.o In gram-positive bacteria there is a thick layer of peptidoglycan (ceil wall) just outside the bacterial cytoplasmic membrane.o This thick wall traps the primary stain (crystal violet) wrhich is not decolorised by ethanol,o In gram-negative bacteria this peptidoglycan (cell wall) layer is thin and just outside this peptidoglycan layer is outer cell membrane (which is not present in gram positive bacteria),o This outer cell membrane is partially dissolved by ethanol, thus washing out the crystal violet and allowing the counterstain to take.