논문 상세보기
Background : Endophytes are generally regarded as beneficial microorganisms that live in plant tissues without disease symptoms. The endophytic species may differ depending on the plant age, the sampled time, the plant genotype, and the tissue. Although numerous endophytes have been identified from various plants, little is known about the endophytic bacteria of Panax quinquefolius, a useful herb plant. Therefore, the aim of this study is to investigate diversity and distribution of endophytic bacteria from 2-years-old to 6-years-old P. quinquefolius and to evaluate antimicrobial activity of isolates.
Methods and Results : Initially, 2-years-old to 6-years-old plants were collected and sterilized with 70% ethanol and sodium hypochlorite, subsequently we prepared individual suspensions which were mixed with sample and sterile distilled water. A total of 88 single colonies were obtained from the LB agar plates spreading suspension. Using 16S rDNA sequencing, the taxonomic status of the isolates were determined consequently 42 species were identified. The 42 species were classified into 4 phylum; Proteobacteria (64%), Firmicute (27%), Actinobacteria (8%), and Bacteroidetes (1%). Based on age, the isolates of 5-years-old plant showed highest diversity. Moreover, Actinomycetales, Bacillales, and Pseudomonadales were equally dispersed as predominant orders in 5-years-old plant. The antagonistic activities of isolates against a phytopathogen, Pseudomonas syringae pv. tomato DC3000 : GFP (Pst : GFP) were performed using dual culture assays. We measured antibacterial activity by quantifying fluorescence of Pst:GFP which representing pathogen growth. As a result, 36 isolates inhibited growth of Pst:GFP. Interestingly, all species belonging Pseudomonas in this study showed strong antibacterial activity against Pst : GFP.
Conclusion : These results improve our understanding of the structure and diversity of the endophytic bacteria of P. quinquefolius. Furthermore, we suggest that bacterial endophytes with antimicrobial activity might have useful as materials for biocontrol agents.
