Himalayan bacterial endophytes enhance microalgal cell numbers and chlorophyll content in synthetic co-culture

Endophytic bacteria associated with medicinal plants from Himalayan mountains possess great biotechnological potential. However, the influence of these Himalayan bacterial endophytes (HBE) on microalgal-promotion and metabolite production is still largely unknown. In this study, the interactions between two endophytic bacterial isolates of an endangered Himalayan medicinal plant and long-chain fatty acids accumulating green alga Micractinium sp. GA001 are characterized in synthetic co-culture systems. The endophytes Staphylococcus pasteuri PPE11 and Yersinia enterocolitica PPE118 significantly enhance microalgal cell numbers with 56% and 49% increase in total chlorophyll content, respectively. Co-culturing microalgae with these endophytes demonstrated distinct responses toward photosynthesis at different temperatures. Endophytes were metabolically active for an extended time (more than 28 days) in co-culturing. The findings were further complemented with genomics studies of endophytes which were subjected to multiple sequencing approaches to assemble and annotate their genomes, resulting in key genes involved in PGP activities, metabolites production and transportation being identified. This study expands the benefits and bioprocessing potential of endophytes of Himalayan medicinal plants.