The periplasmic space is the space seen between the plasma membrane and the outer membrane in the gram-negative bacteria. A very small periplasmic space between the plasma membrane and the peptidoglycan layer (cell wall) may be observed in the gram-positive bacteria (Zuber et al., 2006). The periplasmic space is a lot thicker in Gram negative bacteria. Periplasmic space may be filled with a loose network of peptidoglycan and may constitute up to 40% of the total cell volume. This space is involved in various biochemical pathways including nutrient acquisition, synthesis of peptidoglycan, electron transport, and alteration of substances toxic to the cell. Gram-positive bacteria do not have as many periplasmic proteins compared to the gram-negative bacteria. Instead gram-positive bacteria secrete enzymes which would normally be found in the periplasmic space of the gram-negative bacteria. This secreted enzyme is referred to as an exoenzyme. Substance that occupies the periplasmic space is referred to as a periplasm.

The periplasmic space is of particular clinical importance in that it is the site, in some species, that contains beta-lactamase, an enzyme responsible for degrading the penicillin group of antibiotic drugs, leading to penicillin resistance.

References: – D. White, The Physiology and Biochemistry of Prokaryotes, Oxford University Press, Oxford, 2000, pp. 22. – 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. Sept.;188 (18):6652-60

de:Periplasmatischer Raum