Gram Stain Differential stain (Hans Christian Gram, a Danish doctor ).He developed a new method to stain bacteria so they can bevisible in specimen samples. Differentiate bacteria into two large groups (the GramPositive and the Gram negative). Gram status is important in medicine; the presence orabsence of a cell wall will change the bacterium'ssusceptibility to some antibiotics. Almost all bacteria are described by their Gram stain characteristics.
Based on differences of Cell wall structures Classifies bacteria into 2 large groups: Gram-positive and Gram-negative. Gram-positive bacteria have a thick mesh-like cell wall made of 50% to 90% peptidoglycan, while Gram-negative bacteria only have around 10% of their cell wall made up of peptidoglycan. Gram Positive & Negative Bacteria Reagents for Gram Stain
Crystal Violet (purple). Primary stain; positive stain Stains cell wall purple Iodine Mordant Combines with primary stainto form an insoluble complexthat gets trapped inbacterialcell wall Staining the slide: Start with a heat-fixed slide of your material. Recall, Gram positive bacteria have a single cell membrane and hardy outer cell wall made of peptidoglycan. In contrast. Gram negative cells have two membranes. In between the two membranes is the *periplasmic space* which contains a layer of peptidoglycan.