Structure and functions of the cell envelope of gram-negative bacteria

The surface of gram-negative bacteria contains structures that prevent the entry of noxious compounds into the cell and that help the cell evade recognition by host elements such as antibodies and complement while allowing the bacteria to obtain nutrients from the environment and to attach to structures of the host cell. This review discusses the role of outer-membrane components such as lipopolysaccharides and porin, as well as appendages such as capsules and fimbriae in such functions.