Genetic diversity of bacteria in bioremediation system of iron mine tailing by Robinia pseudoacacia - Ryegrass - Trifolium repens

Abstract

To exploration the change of microorganism in iron tailing sand restoration, a bioremediation system of iron tailing sand by combination of Robinia pseudoacacia - Ryegrass-Trifolium repens pus soil or bio-matrix flowerpot was designed, the change of bacterial quantity and genetic diversity at different time was determined. The tailings and soil samples C1 (tailings), C2 (tailings adjacent to biologic pot) and C3 (Robinia pseudoacacia rhizosphere soil), were collected on the 180th d, 270th d and the 360th d. The bacterial quantity was determined, the bacterial strains were isolated and purified, and genetic diversity was studied by BOXA1R-PCR and 16S rDNA sequencing. The results showed that along the restoration time increasing, the number of bacteria in C2 and C3 increased from 4.81×105 cfu·g−1 and 11.82×105 cfu·g−1 to 5.99×105 cfu·g−1 and 15.67×105 cfu·g−1 at 270th d, then to 8.96×105 cfu·g−1 and 21.96×105 cfu·g−1 at 360th d, respectively, while there was little change in C1. From these samples, a total of 32, 46 and 52 bacterial strains were isolated, and the genetic diversity was determined by BOXA1R-PCR, the results showed that there were 7, 9 and 10 BOXA1R groups formed, respectively; phylogenetic analysis of representatives suggested that genus Bacillus were the predominant, and bacteria with biological nitrogen fixation ability, distributed in Rhizobium, Ensifer, Azotobacter, etc. were founded during the iron tailing sand bioremediation. The results suggests that bio-matrix flowerpot combining Robinia pseudoacacia - Ryegrass - Trifolium repens cultivar can increase the bacterial quantity and genetic diversity in iron tailing sand significantly, and probably has a good application potential for tailings restoration.