These bacterial cells possess chemical structures with acidic protoplasm and a thick peptidoglycan layer. Techoic acids, intertwined among peptidoglycan and techoic acids, are the prominent surface antigen determinants. 

Tulane University

Differential stains add different colors to bacterial structures. 
Two most common differential stains are the gram stain, developed by Christian Gram as a method of staining bacteria in tissues, and the acid fast stain 

Differential Stains

Al-mohanna, Moshtaq & H., quine. (2016). MORPHOLOGY AND CLASSIFICATION OF BACTERIA. 

Morphology and Classification of Bacteria

Gram Positive Cells

Gram negative cells, rich in lipids, have cellular membranes composed of phospholipids, proteins and lipopolysaccharides (LPS). Gram negative cells have a thin peptidoglycan layer without teichoic acids. The outer membrane has lipopolysaccharide channels that transport solutes. Lipoproteins cross link the outer membrane and the peptidoglycan layer. 

Gram Negative Cells

Reactions to gram stains relates to the permeability of the cell wall and cytoplasmic membrane to the iodine complex. Gram negative cells permit the outflow of this dye complex during the removal of the stain. Gram staining is an essential procedure to differentiate bacteria and study morphological bacterial structures. 

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