) Folate-producing rhizobacteria of Hippophaerhamnoides L. from Indian trans-Himalaya low atmospheric zone

Hippophae rhamnoides L. is a plant of immense ethnopharmacological importance and is a known source for various valuable biochemicals and nutraceuticals. The production of folate, a vitamin involved in several vital functions, in this plant is rather poorly understood. Herein, we investigate the hypothesis that rhizobial bacteria serve the plant in this essential vitamin’s biosynthesis. Bacterial strains of Bacillus, Azorhizobium, Frankia, Paenibacillus, Brevibacillus and Pseudomonas, were isolated from the rhizosphere of the plant. HPLC and LCMS were used to trace the production of intra and extra-cellular folate by representative rhizospheric bacterial strains in vitro. From the seventeen functionally characterized bacterial strains of the plant’s rhizosphere, thirteen produced significant amounts of folate. Azorhizobium BR5401 produced the maximum amount of folic acid (424 µg/mL), and Bacillus GY779 was the only strain capable of producing both intracellular and extra-cellular folic acid. The Open Reading Frame coding for dihydroneopterin aldolase, an enzyme involved in folate biosynthesis, was found in one of the representative isolates. Our experimental findings help us to suggest that the folate synthesized by rhizobial bacteria is transported to the plant, highlighting a significant benefit of coexistence.