Osmoregulation in the periplasm
Résumé
The only periplasmic components whose synthesis was found to be induced by low osmotic pressure in various bacterial species are osmoregulated periplasmic glucans (OPGs). OPG structures found in different bacterial species share several common characteristics: (i) D-glucose is the only constituent sugar; (ii) glucose units are linked, at least partially, by beta-glycosidic bonds; (iii) there are a limited number of glucose units (5 to 24); (iv) in most cases, but with a few exceptions, OPG concentration in the periplasm increases in response to a decrease of environmental osmolarity. OPGs appear to be important intrinsic components of the gram-negative bacterial envelope, which can be essential in extreme conditions found in nature, especially when bacteria must interact with a eucaryotic host. Nevertheless, the fundamental function of these compounds remains to be established.