Gram positive bacteria: Gram-positive bacterium

Gram-positive bacterium , any of various types of bacteria that are characterized by having a thick peptidoglycan cell wall and by the absence of an outer membrane composed of lipopolysaccharide. Gram-positive bacteria are a group of bacteria that retain the crystal violet stain in the Gram stain test , appearing purple under a microscope. They have a thick peptidoglycan layer in their cell wall, which contributes to their ability to retain the stain. Gram Positive bacteria are a large and diverse group of microorganisms that are characterized by their ability to retain a crystal violet stain when subjected to the Gram stain protocol. Principle of Gram Staining When the bacteria is stained with primary stain Crystal Violet and fixed by the mordant, some of the bacteria are able to retain the primary stain and some are decolorized by alcohol. The cell walls of gram positive bacteria have a thick layer of protein-sugar complexes called peptidoglycan and lipid content is low.