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 mechanisms that regulate compatible solute accumulation in the enteric bacteria. In this group of organisms the major compatible solutes are betaine, proline and trehalose. Each of these can be synthesised by some members of the enteric group, but only betaine and proline can be accumulated via transport mechanisms. The accumulation of each of the compatible solutes is regulated at the level of gene expression and at the level of the activity of enzymes and transport systems. Potassium glutamate is accumulated by cells growing in media of low to moderate osmolarity. It is believed that high levels of potassium glutamate act as a trigger for the induction of genetic systems required for osmoadaptation, but its role in regulating enzyme and transport systems is less clear. In this review we seek to identify key factors involved in changing the physiology of cells exposed to different degrees of osmotic stress. The fundamental point to be made is that the interplay between compatible solutes and potassium glutamate is central to cell physiology and, therefore, that an understanding of the mechanisms of regulation of compatible solute accumulation is of major consequence for the food industry.