Periplasmic space
The periplasm is a space bordered by two selective permeable barriers, i.e. biological membranes, which are the inner membrane (i.e. cytoplasmic membrane) and the outer membrane in Gram-negative bacteria. Sensu stricto, there is no periplasmic space in Gram-positive bacteria because there is only one biological membrane, the cytoplasmic membrane, but a region termed inner wall zone (IWZ) has been observed between the cytoplasmic membrane and the mature cell wall.[1][2] The periplasm may constitute up to 40% of the total cell volume in Gram-negative species, whereas the IWZ is drastically smaller in Gram-positive species.[3] Composition of the IWZ has not been as yet clearly determined.
It is worth noting here that the description of bacteria as Gram-positive or Gram-negative can be somewhat ambiguous as it can refer to three distinct criterion (staining result, cell-envelope organization, taxonomic group), which are not necessarily met at once for some bacterial species.[4] When referring to the type of bacterial cell enveloppe, the terms of monoderm and diderm bacteria are much more appropriate,[4] where the diderm bacteria can even be further differentiated between diderm–LPS and diderm–mycolate, at least.[5]
In diderm bacteria, the periplasm contains a thin cell wall composed of peptidoglycan. In addition, it includes solutes such as ions and proteins, which are involved in wide variety of functions ranging from nutrient binding, transport, folding, degradation, substrate hydrolysis, to peptidoglycan synthesis, electron transport, and alteration of substances toxic to the cell (xenobiotic metabolism).[6] Importantly, the periplasm is devoided of ATP.
[edit] References
- ^ , Matias, V. R., and T. J. Beveridge. 2005. Cryo-electron microscopy reveals native polymeric cell wall structure in Bacillus subtilis 168 and the existence of a periplasmic space. Mol. Microbiol. 56:240-251. doi:10.1111/j.1365-2958.2005.04535.x.
- ^ , Zuber B, Haenni M, Ribeiro T, Minnig K, Lopes F, Moreillon P, Dubochet J. 2006. Granular layer in the periplasmic space of Gram-positive bacteria and fine structures of Enterococcus gallinarum and Streptococcus gordonii septa revealed by cryo-electron microscopy of vitreous sections. J Bacteriol. 188:6652-6660. doi:10.1128/JB.00391-06
- ^ Otto Holst; Guntram Seltmann. The Bacterial Cell Wall. Berlin: Springer. ISBN 3-540-42608-6.
- ^ a b , Desvaux M, Hébraud M, Talon R, Henderson IR. 2009. Secretion and subcellular localizations of bacterial proteins: a semantic awareness issue. Trends Microbiol. 17:139-145. doi:10.1016/j.tim.2009.01.004
- ^ , Sutcliffe IC. 2010. A phylum level perspective on bacterial cell envelope architecture. Trends Microbiol. 18:464-470. doi:10.1016/j.tim.2010.06.005
- ^ Klein, Donald W.; Prescott, Lansing M.; Harley, John (2005). Microbiology. Boston: McGraw-Hill Higher Education. ISBN 0-07-295175-3.
[edit] Further reading
- D. White, The Physiology and Biochemistry of Prokaryotes, Oxford University Press, Oxford, 2000, pp. 22.
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