Gram-positive bacteria are those that are stained dark blue or
violet by Gram staining. This is in contrast to Gram-negative
bacteria, which cannot retain the crystal violet stain, instead
taking up the counterstain (safranin or fuchsine) and appearing
red or pink. Gram-positive organisms are able to retain the
crystal violet stain because of the high amount of peptidoglycan
in the cell wall. Gram-positive cell walls typically lack the
outer membrane found in Gram-negative bacteria. The following
characteristics are generally present in a Gram-positive
bacterium: - cytoplasmic lipid membrane - thick peptidoglycan
layer - capsule polysaccharides (only in some species) -
flagellum (only in some species) - if present, it contains two
rings for support as opposed to four in Gram-negative bacteria
because Gram-positive bacteria have only one membrane layer. -
The individual peptidoglycan molecules are cross-linked by
pentaglycine chains by a DD-transpeptidase enzyme. In gram-
negative bacteria, the transpeptidase c