<unk>  bacteria are those that do not retain crystal violet dye in the<unk>  staining protocol.<unk> -positive bacteria will retain the dark blue dye after an alcohol wash. In a<unk>  stain test, a counterstain (commonly Safranin) is added after the crystal violet, colouring all<unk>  bacteria a red or pink colour.  The test itself is useful in classifying two distinctly different types of bacteria based on structural differences in their cell walls.
Many species of<unk>  bacteria are pathogenic, meaning they can cause disease in a host organism. This pathogenic capability is usually associated with certain components of<unk>  cell walls, in particular the lipopolysaccharide (also known as LPS or endotoxin) layer.  The LPS is the trigger which the body's innate immune response receptors sense to begin a cytokine reaction.  It is toxic to the host. It is this response which begins the inflammation cycle in tissues and blood vessels.
Gram-negative
Gram-positive
Acid-fast
Liquid
Hydrophobe
Pedunculated
RNA virus
Aerobic organism