The Cell Envelope
Alexander Hahn and Enrico Schleiff
from: The Cell Biology of Cyanobacteria (Edited by: Enrique Flores and Antonia Herrero). Caister Academic Press, U.K. (2014)
Cyanobacteria are prokaryotes with cell envelopes typical for Gram-negative bacteria. The cell envelope consists of four distinct layers, the plasma membrane, the peptidoglycan layer, the outer membrane and in some cases the surface or S-layer. Often, the latter three are referred to as the cell wall. The functionality of the cell envelope is defined by the cooperative action of lipids and membrane-embedded proteins. The membranes of cyanobacterial species contain two types of lipids, phosphoglycerolipids and galactolipids. The proteins of the plasma membrane show the typical α-helix based membrane domain architecture, whereas the proteins in the outer membrane have a β-barrel shaped membrane domain. The proteins perform many distinct functions ranging from solute transport to signal transduction. Thus, several features are indeed comparable between the cyanobacterial and the proteobacterial systems investigated so far. However, some properties are unique for the cyanobacterial branch. In this chapter, we summarize the current knowledge on composition, structure and function of the cell envelope including information obtained from different cyanobacterial strains. We also compare the properties of the cyanobacterial envelope to those of non-photosynthetic Gram-negative bacteria read more ...