Bioremediation of Copper and Nickel from Freshwater Fish Cyprinus carpio Using Rhiozoplane Bacteria Isolated from Pistia stratiotes

The use of metal hyper-accumulator plants and the bacteria associated with them to remove metals from the environment is an emerging technology to control bioaccumulation of metals in living organisms. In this study, three copper (Cu) and nickel (Ni) resistant bacteria were isolated from roots of the aquatic plant Pistia stratiotes. These strains were identified as Stenotrophomonas maltophilia KUGK115 (S1), Comamonas aquatica KUGK120 (S2) and S. maltophilia KUGK130 (S3) using 16SrDNA sequence analyses. All the strains were found efficient in accumulating a high concentration of Cu and Ni in their cell mass. Two-week experiments were conducted with the freshwater fish Cyprinus carpio with the three bacterial strains and P. stratiotes in different combinations. They revealed that inoculation of fish culture system with a single culture of the strain S3 reduced accumulation of both Cu and Ni in C. carpio more efficiently than the other two strains or a mixture of the three strains. Polynomial regression analyses revealed that bioaccumulation of Cu in C. carpio was further reduced, while bioaccumulation of Ni was increased when the fish rearing system received a culture of S3 along with the plant P. stratiotes. This study reveals that the bacterial strain S3 is more efficient in reducing bioaccumulation of Ni than Cu in C. carpio and roots of P. stratiotes. It is concluded that inoculation of the fish culture system with a pure culture of the rhizoplane bacterial strain Stenotrophomonas maltophilia KUGK130 (S3) can be an efficient management system to control bioaccumulation of Cu and Ni in freshwater fish.