An iodine stain solution is applied to the cells. The slide is then washed with alcohol . Finally, the cells are restained with a pink dye solution called safranin . Gram-positive bacteria have a thick peptide layer, retain the crystal violet, and appear purple when viewed under a microscope. Gram-negative bacteria have a thin peptide layer, take up the pink stain, and appear pink when viewed under a microscope.
Many antibiotics have no effect on gram-negative bacteria.
Cell wall - some rigid and others flexible. Cell membrane - same as other cells. Cytoplasm - same as other cells. DNA - a single, circular chromosome located in the cytoplasm. Remember, bacteria cells do not have a nucleus.