Isolation and Characterization of Paenibacillus peoriae JC-3jx: An Endophytic Bacterium from Dendrobium nobile with Antibacterial and Growth-Promoting Potential

Abstract Dendrobium is an important source of natural components with high medicinal value. While numerous endophytic fungi associated with these plants have been extensively studied, research on endophytic bacteria remains limited. In this study, an improved tissue separation method was used to isolate endophytic bacteria from Dendrobium nobile and enrich the resources of high-quality biocontrol bacteria with both antibacterial and growth-promoting effects. We assessed the inhibitory effect of the isolated bacteria on pathogenic bacteria and fungi using agar diffusion and plate confrontation methods. We further investigated the growth-promoting effect of bacterial suspensions at various concentrations on corn seeds and Dendrobium nobile plantlets. The obtained endophytic bacterium, JC-3jx, isolated for the first time from the stem of Dendrobium nobile, exhibited significant inhibitory activity against the tested indicator bacteria. Morphologic and phylogenetic analysis confirmed the closest similarity of JC-3jx to Paenibacillus peoriae, leading to its final identification as Paenibacillus peoriae JC-3jx. This bacteria exhibited varying degrees of inhibition against the six pathogenic plant fungi tested, achieving a significant 56% inhibition rate against Pyricularia oryzae. Furthermore, the sterile fermentation supernatant of JC-3jx demonstrated pronounced inhibitory activity against the three tested pathogenic bacteria, particularly the gram-negative Escherichia coli. Moreover, the results demonstrate that the bacterial suspension of JC-3jx significantly promoted the rooting of corn seeds and the growth of Dendrobium nobile plantlets, indicating its excellent antibacterial and growth-promoting potential.