Periplasmic space

The periplasmic space or periplasm is a space between the inner cytoplasmic membrane and external outer membrane of Gram-negative bacteria. It may constitute up to 40% of its total cell volume.cite book |author=Otto Holst; Guntram Seltmann |title=The Bacterial Cell Wall |publisher=Springer |location=Berlin |year= |pages= |isbn=3-540-42608-6 |oclc= |doi=] The space contains a loose network of murein peptidoglycan chains, as well as a gel containing hydrolytic and degradative enzymes.cite book |author=Kenneth J. Ryan; C. George Ray |title=Sherris Medical Microbiology: An Introduction to Infectious Diseases |publisher=McGraw-Hill Medical Publishing Division |location=New York |year=2004 |pages= |isbn=0-8385-8529-9 |oclc= |doi=] Other enzymes in the gel are involved in various biochemical pathways including peptidoglycan synthesis, electron transport, and alteration of substances toxic to the cell (xenobiotic metabolism).cite book |author=Klein, Donald W.; Prescott, Lansing M.; Harley, John |title=Microbiology |publisher=McGraw-Hill Higher Education |location=Boston |year=2005 |pages= |isbn=0-07-295175-3 |oclc= |doi=] In some species, the gel also contains beta-lactamase, an enzyme responsible for degrading penicillin. This can be of clinical importance when considering antibiotic resistance.

Since Gram-positive bacteria have no equivalent space, the enzymes they produce which would normally be retained in the periplasmic space of a Gram-negative bacterium are instead secreted into the external environment. These secreted enzymes are referred to as exoenzymes.

References

Further reading

* D. White, The Physiology and Biochemistry of Prokaryotes, Oxford University Press, Oxford, 2000, pp. 22.