Characterization of a copper-resistant symbiotic bacterium isolated from Medicago lupulina growing in mine tailings

摘要

A root nodule bacterium, Sinorhizobium meliloti CCNWSX0020, resistant to 1.4mM Cu~(2+) was isolated from Medicago lupulina growing in mine tailings. In medium supplied with copper, this bacterium showed cell deformation and aggregation due to precipitation of copper on the cell surface. Genes similar to the copper-resistant genes, pcoR and pcoA from Escherichia coli, were amplified by PCR from a 1.4-Mb megaplasmid. Inoculation with S. meliloti CCNWSX0020 increased the biomass of M. lupulina grown in medium added 0 and 100mgCu~(2+)kg~(-1) by 45.8% and 78.2%, respectively, and increased the copper concentration inside the plant tissues grown in medium supplied with 100μM Cu2+ by 39.3%, demonstrating that it is a prospective symbiotic system for bioremediation purposes.