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 in control, hypersaline, and non-ionic hyperosmotic media. Results indicated that the effects of hyperosmolarity on the synthesis and the degradation of the disaccharide were diverse. In the salt-tolerant slow-growing strain Bradyrhizobium sp. ATCC 10317, we observed increased synthesis and accumulation of trehalose under hyperosmolarity imposed by either NaCl or PEG-8000. In the other two peanut rhizobia strains, the disaccharide level did not change under hypersalinity. In the salt-sensitive slow-growing strain Bradyrhizobium sp. USDA 3187, intracellular trehalose diminished in late stationary phase-cells grown with PEG, this reduction was accompanied by both an increased 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 trehalase activity, afterwards, the activity of synthetic enzymes augmented.