IMMUNOLOGY

Detailed explanation-1: -Gram-positive bacteria have cell walls that contain thick layers of peptidoglycan, a substance that forms the cell walls of many bacteria. The peptidoglycan forms about 90% of the cell wall in gram-positive bacteria. This causes them to appear blue to purple under a Gram stain.

Detailed explanation-2: -Gram-positive organisms are either purple or blue in color, while gram-negative organisms are either pink or red in color. Bacilli are rod-shaped, while cocci are spherical.

Detailed explanation-3: -The Gram positive cell looses some of its large chunky peptidoglycan cell wall but keeps enough of it to retain the purple colour. The Gram negative cell has its outer membrane and small peptidoglycan layer completely stripped away, leaving it colourless.