MECHANISMS CONTROLLING COMPATIBLE SOLUTE ACCUMULATION - A CONSIDERATION OF THE GENETICS AND PHYSIOLOGY OF BACTERIAL OSMOREGULATION

This paper seeks to review briefly the current understanding of the me chanisms that regulate compatible solute accumulation in the enteric b acteria. In this group of organisms the major compatible solutes are b etaine, proline and trehalose. Each of these can be synthesised by som e members of the enteric group, but only betaine and proline can be ac cumulated via transport mechanisms. The accumulation of each of the co mpatible solutes is regulated at the level of gene expression and at t he level of the activity of enzymes and transport systems. Potassium g lutamate is accumulated by cells growing in media of low to moderate o smolarity. It is believed that high levels of potassium glutamate act as a trigger for the induction of genetic systems required for osmoada ptation, but its role in regulating enzyme and transport systems is le ss clear. In this review we seek to identify key factors involved in c hanging the physiology of cells exposed to different degrees of osmoti c stress. The fundamental point to be made is that the interplay betwe en compatible solutes and potassium glutamate is central to cell physi ology and, therefore, that an understanding of the mechanisms of regul ation of compatible solute accumulation is of major consequence for th e food industry.