An Overview of Biological Basics - Bioprocess Engineering: Kinetics, Biosystems, Sustainability and Reactor Design - page 30

FIGURE 2.5 Schematic of a typical gram-negative bacterium. A gram-positive cell is similar, except that it has no outer membrane, its peptidoglycan
layer is thicker, and the chemical composition of the cell wall differs significantly from the outer envelope of the gram-negative cell.