Bacterial cell walls

Bacterial cell walls

The rigid cell walls of bacteria determine cell shape and prevent the cell from bursting as a result of osmotic pressure. The structure of their cell walls divides bacteria into two broad classes that can be distinguished by a staining procedure known as the Gram stain, developed by Christian Gram in 1884. Gram-negative bacteria (such as E. coli) have a dual membrane system, in which the membrane plasma is surrounded by a permeable outer membrane. These bacteria have thin cell walls located between their inner and outer membranes. In contrast, Gram-positive bacteria (such as the common human pathogen Staphylococcus aureus) have only a single plasma membrane, which is surrounded by a much thicker wall cell.

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