What is the composition of the cell envelope?

The bacterial cell envelope provides the cell with structural integrity. There are two types of bacterial cell envelopes: Gram-positive cell envelope and Gram-negative cell envelope. 

Gram-Positive Cell Envelope

The cell envelope of gram-positive bacteria is made up of a thick cell wall, cytoplasmic membrane, and capsule. The cell wall is composed of a thick peptidoglycan layer that is embedded with teichoic acids and lipoteichoic acids.

Gram-negative Cell Envelope

The cell envelope of gram-negative bacteria is made up of a thin cell wall, cytoplasmic membrane, outer membrane, periplasmic space, and capsule. The cell wall is composed of a thin peptidoglycan layer. The outermost layer is made up of lipopolysaccharides and phospholipids.

Mycobacteria Cell Envelope

Mycobacteria have a cell wall that is different from that of both gram-positive and gram-negative bacteria. The outer cell membrane is absent in mycobacteria but there is a cell wall that is composed of peptidoglycan, mycolic acid, and arabinogalactan.