Rhizosphere Bacillus proteolyticus Strain Enhances the Eleutherococcus senticosus (Rupr. & Maxim.) Maxim. Growth in Roots and Soil Nutrient Status While Enriching the Plant-Beneficial Bacteria in Rhizosphere

Simple SummaryThis study explored howBacillus proteolyticus(B. proteolyticus) helps the root development ofEleutherococcus senticosus(Rupr. and Maxim.) Maxim. (therm E. senticosus). The researchers usedtherm E. senticosusseeds and watered the soil with different concentrations ofB. proteolyticussuspension. Results showed that after usingB. proteolyticus, the seed germination rate, number of root tips, total root length and total root volume oftherm E. senticosusfirst increased and then decreased. The 50% concentration ofB. proteolyticuswas best for seed germination. Compared with the control group, this concentration led to 16 different substances related to plant metabolism and an increase in the content of six main medicinal components. It also increased two types of nitrogen in the soil around roots and the amount of a specific kind of bacteria, which were all related to better root growth. This study found that 50%B. proteolyticuscan promotetherm E. senticosusgrowth, root development, and its medicinal quality. These bacteria can be made into a useful biological product. The study suggests using 50%B. proteolyticussuspension to growtherm E. senticosus, which can increase its yield and medicinal value, providing a sustainable way for its agricultural production.This study aimed to investigate the promoting mechanisms ofBacillus proteolyticus (B. proteolyticus)onEleutherococcus senticosus(Rupr. and Maxim.) Maxim. (therm E. senticosus) root development. Usingtherm E. senticosusseeds as experimental material, soil was drenched withB. proteolyticussuspensions at different concentrationsv/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 mm3) exhibited an initial increase, then a decrease afterB. proteolyticustreatment (p< 0.05). Principal component analysis (PCA) indicated that the soil ofB. proteolyticusat 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. proteolyticustreatment. 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 NO3−-N and NH4+-N were promoted, and the abundance ofGemmatimonadeteswas increased in bacterial communities. Correlation analysis revealed significant correlations between the abundance ofGemmatimonadetesand the contents of NO3−-N and NH4+-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 ofB. proteolyticusat a 50% concentration could enhance both the biomass and medicinal value of cultivatedtherm E. senticosus. This study provided novel insight thatB. proteolyticuswould be expected to be developed as an effective microbial preparation, offering a sustainable strategy for its agricultural production.