Host specificity determines the assemblage of root endophytic bacteria of plants growing in metal contaminated soil
The diversity of endophytic bacteria colonizing the roots of an invasive plant, a pioneer plant, and an endemic plant from varied plant communities developing in a lead-zinc mine tailing pond, southwestern China, was analyzed by the culture-independent method. A total of 1650 16S rDNA sequences were screened for the establishment of four clone libraries, from the pure stands of Arthraxon hispidus (LS-Ah) and Ageratina adenophora (LS-Aa), and a mixed stand of A. adenophora (LC-Aa) and Alnus
... -Aa) and Alnus nepalensis (LC-An) (co-dominant community), respectively. Phylogenetic analysis revealed that the sequences were clustered into at least 17 phylogroups, which consisted of alpha, beta, gamma, delta subclasses of the Proteobacteria, Tenericutes, Bacteroidetes, Chloroflexi, Actinobacteria, Spirochaetes, Chlamydiae, Firmicutes, Deinococcus-Thermus, Planctomycetes, Nitrospirae, Gemmatimonadetes and unclassified bacteria Candidatus Saccharibacteria. The dominant phylum was Proteobacteria (50.49% of the total clones), and the dominant genus was Candidatus Phytoplasma (19.94% of the total clones). The invasive plant (A. adenophora) accumulated more parasitic endophytic bacteria (Phytoplasma) than the other two native plants. Phylogenetic structures of the four 16S rDNA clone libraries were distinct with their similarity indices being less than 0.5. The results also revealed that the dominant phyla and dominant genera in the four clone libraries varied a lot, and the endemic grass harbored a higher diversity of endophytic bacteria than the pioneer and invasive plants, the host-specificity took a more important role in shaping the endophytic bacteria community than the habitats in the metal stressed environment.