The study on the design and regulatory effects of synthetic communities of endophytic actinomycetes of Salvia miltiorrhiza Bunge

Microorganisms can confer or enhance various ecological adaptation functions of host plants, offering wide-ranging applications in the cultivation and production of medicinal plants. While root-associated beneficial actinomycetes are commonly used in biological control, their effects on plant growth and development have been rarely reported. This study focuses on a total of 13 beneficial endophytic actinomycetes in the roots of Salvia miltiorrhiza Bunge. Under different synthetic community (SynCom) construction principles, we constructed five synthetic communities based on functions and relationships to investigate their effects on growth, nitrogen metabolism, phosphorus metabolism, iron metabolism, resistance, and active components of S. miltiorrhiza. Synthetic communities 3 and 4 composed of functionally complementary strains promoted growth more effectively, synthetic communities 1 and 3 composed of distantly related strains increased total phenolic acid content, and synthetic community 5 that composed solely of indole-3-acetic acid (IAA)-producing strains not only promoted growth but also enhanced the active component content. Genome analysis revealed that synthetic communities with terpenes biosynthetic gene clusters promoted S. miltiorrhiza growth. Our results suggested synthetic community design should consider strain relationships, plant growth-promoting (PGP) traits, and functional genes. This study introduces novel insights into synthetic community design.