Actually, there is much more to the cell wall than appears in Figure 4.6. There are two fundamental types of bacterial cell walls: Gram-positive cell walls, and Gram-negative cell walls. These two cell wall-types can be differentiated by using a Gram stain, which results in Gram-positive bacteria staining a deep purple, and Gram-negative organisms staining a pink or red. This difference in cell wall structure results in more than just color differences when bacteria are Gram-stained, however. Knowledge of the cell wall type can enable prediction of other characteristics such as sensitivity to certain antibiotics, production of toxins, and susceptibility to disruption by different environmental agents. Understanding such differences begins with knowledge of the structural differences between these two cell wall types.