Endophytic bacteria have been found in virtually every plant studied, where they colonize the internal tissues of their host plant and can form a range of different beneficial relationships. The diversity of bacterial endophytes associated with ginseng plants of varying age levels in Korea was investigated. Fifty-one colonies were isolated from the interior of ginseng stems. Although a mixed composition of endophyte communities was recovered from ginseng based on the results of 16S rDNA analysis, bacteria of the genus Bacillus and Staphylococcus dominated in 1-year-old and 4-year-old plants, respectively. Phylogenetic analysis revealed four clusters: Firmicutes, Actinobacteria, α-Proteobacteria, and γ-Proteobacteria, with Firmicutes being predominant. To evaluate the plant growth promoting activities, 18 representative isolates were selected. Amplification of nifH gene confirmed the presence of diazotrophy in only two isolates. Half of the isolates solubilized mineral phosphate. Except four, all the other endophytic isolates produced significant amounts of indole acetic acid in nutrient broth. Iron sequestering siderophore production was detected in seven isolates. Isolates E-I-3 (Bacillus megaterium), E-I-4 (Micrococcus luteus), E-I-8 (B. cereus), and E-I-20 (Lysinibacillus fusiformis) were positive for most of the plant growth promoting traits, indicating their role in growth promotion of ginseng.

The objective of this work was to determine the shifts in the PCR-DGGE profiles of bacterial communities associated with the rhizosphere soil of ginseng at varying age levels. Differences in the dominance of intense DNA bands in the DGGE profile was observed over the age of the plants indicating the fluctuation in the microbial community structure. The bacterial orders of actinomycetales of Actinobacteria and Spingomonadales and Rhizobiales of a-Proteobacteria were predominant in the ginseng soil.

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