Synthesis, accumulation and hydrolysis of trehalose during growth of peanut rhizobia in hyperosmotic media

We examined and compared the activities of synthetic and hydrolytic enzymes involved in trehalose metabolism, in three peanut rhizobia strains grown i n control, hypersaline, and non-ionic hyperosmotic media. Results indicated that the effects of hyperosmolarity on the synthesis and the degradation o f the disaccharide were diverse. In the salt-tolerant slow-growing strain B radyrhizobium sp. ATCC 10317, we observed increased synthesis and accumulat ion of trehalose under hyperosmolarity imposed by either NaCl or PEG-8000. In the other two peanut rhizobia strains, the disaccharide level did not ch ange under hypersalinity. In the salt-sensitive slow-growing strain Bradyrh izobium sp. USDA 3187, intracellular trehalose diminished in late stationar y phase-cells grown with PEG, this reduction was accompanied by both an inc reased activity of synthetic enzymes and a decreased activity of trehalase. In the salt-tolerant fast-growing strain Rhizobium sp. TAL. 1000, we also observed a reduction of intracellular trehalose under PEG-mediated growth, this decrease was early and transiently accompanied by an enhancement of tr ehalase activity, afterwards, the activity of synthetic enzymes augmented.