Bacterial Cytoplasmic Membrane

Abstract

The bacterial cytoplasmic membrane is composed of a phospholipid bilayer and proteins and encloses the contents of the bacterial cell. Hydrophobic in nature, it acts as a barrier, preventing the leakage of the hydrophilic cytoplasmic constituents and protecting the inside of the cell from environmental insult.

Keywords: phospholipid; bioenergetics; respiration; transport; translocation; membrane

Figure 1.

Diversity of Escherichia coli respiratory chain enzymes. The respiratory chain comprises primary dehydrogenases (on the left), quinone species (middle) and terminal reductases (on the right). Expression of enzymes is regulated in response to the presence of reducing substrates and oxidants. Current topological models for the individual enzymes are represented with the cytoplasmic side of the membrane being ‘up’ in the figure. FAD, flavin adenine mononucleotide; FMN, flavin mononucleotide; b, haem b; o, haem o; NAD, nicotinamide adenine dinucleotide; DHAP, dihydroxyactone phosphate; TMAO, trimethylamine‐N‐oxide; DMSO, dimethylsulfide.

Figure 2.

The electron‐transfer chain comprising formate dehydrogenase (FdnGHI, left), a membrane‐intrinsic quinone pool (centre) and nitrate reductase (NarGHI, right). This chain translocates protons by exploiting the scalar distribution of substrate‐binding sites across the cytoplasmic membrane.

Figure 3.

Membrane‐bound transporter systems in the cytoplasmic membrane of bacteria. Metabolites are transported across the cytoplasmic membrane (grey box) by facilitated diffusion (example GlpF, the glycerol facilitator), proton‐coupled permeases (example LacY, the lactose permease), binding protein‐coupled ABC transporters (example HisJ QMP2, the histidine permease) or by group translocation (example the phosphoenolpyruvate phosphotransferase system (PTS)). The F0F1 ATPase complex that generates ATP from the ΔμH+ or consumes ATP to generate ΔμH+ is also shown.

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Further Reading

Gennis RB (1989) Biomembranes: Molecular Structure and Function. New York: Springer‐Verlag.

Harold FM (1986) The Vital Force: A Study of Bioenergetics. New York: Freeman and Co.

Nicholls DG and Ferguson SJ (2002) Bioenergetics 3. London: Academic Press.

Vance DE and Vance JE (1996) Biochemistry of Lipids, Lipoproteins and Membranes. Amsterdam: Elsevier.

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How to Cite close
Weiner, Joel H, and Rothery, Richard A(Dec 2007) Bacterial Cytoplasmic Membrane. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0000299.pub2]