A Study of the Antibacterial Activity and Growth-Promoting Capability of Methylobacterium PjM1 in Panax japonicus Callus Tissue

【Purpose】As the most extensively studied leaf-interface microorganism, Methylobacterium offers significant advantages in promoting plant growth and increasing yields. Panax japonicus, a traditional Chinese medicinal herb, thrives in environments teeming with diverse microorganisms. Isolating Methylobacterium from Panax japonicus allows for the screening of strains that significantly enhance its growth.【Method】Strains were screened using methanol-supplemented medium and identified via Gram staining and 16S rDNA sequencing. The bacteriostatic activity of the isolated strain was assessed using the well-plate method, and its effect on plant growth was evaluated through Arabidopsis thaliana growth promotion experiments.【Results】A pink-colored Methylobacterium strain was screened using a methanol-supplemented medium. The strain was identified as belonging to the genus Methylobacterium through Gram staining and 16S rDNA sequencing and was designated PjM1. Tests of PjM1's antimicrobial activity and growth-promoting potential revealed that the strain exhibited antimicrobial activity against Bacillus subtilis, with an average inhibition zone diameter of 8 mm; however, it showed no activity against Escherichia coli or Staphylococcus aureus. PjM1 metabolites showed no inhibitory activity against E. coli, S. aureus, or B. subtilis. PjM1 accelerated Arabidopsis thaliana seed germination and promoted the development and growth of both primary and lateral roots in seedlings, with a more pronounced effect on primary root development. Inoculation with strain PjM1 significantly increased carotenoid and chlorophyll content in Arabidopsis thaliana.【Conclusion】Overall, research indicates that PjM1 possesses remarkable growth-promoting potential and could be used to develop Methylobacterium-based plant growth promoters and biocontrol agents to advance sustainable agriculture.