Half Answer: There are both Gram positive and Gram negative stains that are used to identify different types of Bacteria. They depend upon 'membrane content' - some stains highlight only the nuclear envelope.
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The Gram stain determines the cell wall composition of bacteria. It categorizes bacteria into two groups based on their ability to retain or release a purple dye: Gram-positive bacteria retain the dye and appear purple, while Gram-negative bacteria do not retain the dye and appear pink. This staining technique is commonly used in microbiology to help identify and classify bacteria.
Safranin is used as a counterstain in Gram staining to colorize Gram-negative bacteria, as they do not retain the crystal violet primary stain. This allows for better contrast and differentiation of Gram-negative bacteria against the purple Gram-positive bacteria.
Gram-negative on a Serratia marcescens gram stain means that the bacterium has a cell wall that does not retain the crystal violet stain used in the gram staining procedure. This indicates that Serratia marcescens has a thin peptidoglycan cell wall, and the outer membrane contains lipopolysaccharides.
Methylene blue a basic stain is generally used to identify the external morphology of bacteria.The other stain which is used as differential stain and which can also differentiate the baceteia on the basis of their cell wall is gram stain i.e. Crystal voilet and is counter stained with Saffranine
Gram- negative bacteria turns red to pink after the gram stain is performed.