Abstract
This study aimed to investigate the promoting mechanisms of Bacillus proteolyticus (B. proteolyticus) on Eleutherococcus senticosus (Rupr. and Maxim.) Maxim. (therm E. senticosus) root development. Using therm E. senticosus seeds as experimental material, soil was drenched with B. proteolyticus suspensions at different concentrations v/v (water, 25%; 50%; 75%, and 100%). The results showed that the germination rate, root tip number (52 ± 2.97), total root length (23.7 ± 0.46 cm), and total root volume (57.36 ± 1.64 mm(3)) exhibited an initial increase, then a decrease after B. proteolyticus treatment (p < 0.05). Principal component analysis (PCA) indicated that the soil of B. proteolyticus at a 50% concentration was conducive to seed germination. Compared with CK, GC-MS analysis revealed that 16 differential primary metabolites were screened, primarily enriched in galactose metabolism, starch and sucrose metabolism, and TCA cycle pathways after 50% B. proteolyticus treatment. LC-MS analysis revealed that the contents of six main medicinal components were higher than those of CK, with the content of eleutheroside E being 2.62 times greater. In rhizosphere soil, the contents of NO(3)(-)-N and NH(4)(+)-N were promoted, and the abundance of Gemmatimonadetes was increased in bacterial communities. Correlation analysis revealed significant correlations between the abundance of Gemmatimonadetes and the contents of NO(3)(-)-N and NH(4)(+)-N, as well as between total root length and D-galactose content, suggesting that these relationships may contribute to the root growth. Therefore, the soil of B. proteolyticus at a 50% concentration could enhance both the biomass and medicinal value of cultivated therm E. senticosus. This study provided novel insight that B. proteolyticus would be expected to be developed as an effective microbial preparation, offering a sustainable strategy for its agricultural production.