Bifunctional and metabolically stable Himalayan endophytic bacterium Pantoea sp. enhances microalgal productivity

Due to lack of accessibility to endangered medicinal plants of high-altitude Himalayan Mountains, the biotechnological potential of microorganisms associated with these plants has not been largely explored. Here, we demonstrate bifunctional characteristics of a Himalayan bacterial endophyte Pantoea sp. AHE68 that simultaneously converts inorganic phosphate into organic phosphate (29.8% increase in available phosphorus content) and synthesis growth-promoting IAA (45.34±0.82 μg mL −1 ) thereby enhances microalgal productivity in synthetic co-culture system. Pantoea sp. AHE68, a phosphate solubiliser, originally isolated from endangered medicinal plant Aconitum heterophyllum , simultaneously secretes organic acid (10.42 mM mL −1 ) to convert the inorganic phosphate into organic phosphate as well as produces high level IAA under stress conditions. Interactions of AHE68 and long-chain fatty acids (LCFA) producing microalga Micractinium sp. GA001 were characterised in different combinations of synthetic co-culture systems. The endophyte AHE68 was found to significantly enhance 22.71% and 79.27% increase in microalgal cell numbers and lipid contents in co-culture systems, respectively. In co-culture studies, AHE68 was found to be metabolically capable to simultaneously synthesise active forms of IAA and organic acids under salt-stress conditions. The findings suggest that bifunctional characteristics of AHE68 was metabolically stable for extended period of time (up to 30 days) to improve microalgal productivity. The study expands the industrial importance of these under-explored Himalayan endophytes.