Bacterial diversity in mine tailings compared by cultivation and cultivation-independent methods and their resistance to lead and cadmium

To examine bacterial community composition in rhizosphere of plants colonizing on mine tailings and phylogenetic differences between subcommunities resistant to different metals, we constructed four clone libraries of 16S rDNA sequences. One was amplified directly from tailing microbial DNA (named as Ci library) and three from cultures on the plates containing of 0.5 mM CdCl2 (Cd library), 2 mM Pb (NO3)(2) (Pb library), and without any metals (Cw library). In total, nine bacterial divisions and two unclassified groups were identified from 352 clones of these libraries. Ci clones covered eight divisions, whereas all cultivable clones only covered four divisions. Thus, Ci library provided more phylogenetic diversity than cultivable libraries. However, the microbes represented by the cultivable clones were more similar to previously described bacteria than those represented by Ci clones. All Ci clones were not found in three cultivable libraries. Cd library were exclusively Gram-negative bacteria of Acinetobacter, Ralstonia, Comamonas, and Chryseobacterium. Meanwhile, dominant Gram-positive bacteria in Pb library, Paenibacillus and Bacillus, were also not found in Cd library. Our data indicate that phylogenetic structure was very different from those in acid mine drainage. Meanwhile, tailings harbored phylogenetically distinct subcommunities resistant to Pb and Cd.