IDENTIFICATION OF TREHALOSE AND GLYCINE BETAINE AS COMPATIBLE SOLUTESIN THE MODERATELY HALOPHILIC SULFATE-REDUCING BACTERIUM, DESULFOVIBRIO-HALOPHILUS

Increasing NaCl concentrations in the growth medium inhibited the grow th of Desulfovibrio halophilus due to both an increase in the lag phas e of growth and a reduction in the specific growth rate. Addition of 1 mM glycine betaine to the growth medium partially relieved this inhib ition. Natural abundance C-13 nuclear magnetic resonance spectroscopy identified the disaccharide alpha-alpha trehalose and glycine betaine as the major organic solutes accumulated by D. halophilus during growt h in mineral salts medium and mineral salts medium supplemented with 1 mM glycine betaine, respectively. The presence of a weak glycine beta ine transport system was confirmed by following the accumulation of [m ethyl-C-14]glycine betaine during osmotic upshock. In the absence of e xogenous glycine betaine the intracellular trehalose concentration of D. halophilus was dependent upon the osmolarity of the growth medium, with a maximum concentration of 8.3 mu mol trehalose mg protein(-1) re corded in cultures grown in the presence of 15% w/v NaCl. Intracellula r K+ concentrations were also dependent upon the osmolarity of the gro wth medium over the range 3-9% w/v NaCl, but showed little further inc rease at higher NaCl concentrations.