Bacteria cells have a wall that is primarily responsible for its strength. This wall is made of peptidoglycan. Long chains of peptidoglycan construct a sheet around the cell. These chains, made with covalent bonds, provide rigidity in only one direction and only after cross-linking is the cell will rigid in X and Y directions. Peptidoglycan is only found in Bacteria.

Lysosomes destroy peptidoglycan. Peptidoglycan is composed of N-acetylglucosamine and N-acetylmuramic acid. The bonds between the two sugar derivatives are held together by beta-1,4 glycosidic bonds, which are cleaved by lysosomes.

There are two types of bacteria cells gram positive and gram negative. The former has a cell wall made of 90% peptidoglycan. Many gram-positive bacteria have cells walls composed of several sheets of peptidoglycan. The latter has a cell wall with little peptidoglycan. The amount of peptidoglycan affects the results of a test that differentiates between the two bacteria types. The peptidoglycan in the gram-positive cells are dehydrated by alcohol causing the cell wall pores to close, and the violet colored stain to remain.