29. PLANT-MICROBE SYMBIOSIS FOR BIOREMEDIATION OF HEAVY METAL CONTAMINATED SOIL: PERSPECTIVES FOR BELARUS

摘要

Problems of heavy metal and radionuclide contamination are very important for Belarus. About 23% of its territory is contaminated with radio-nuclides, some areas are heavily contaminated with Cu, Zn, Pb, and Cd. Heavy metals can be carcinogenic and mutagenic even at low doses, are not biodegradable and are easily accumulated by live organisms. Phytoremediation and bioremediation technologies are just beginning to be developed in Belarus. Some research studies in the field of phytostabilization and phytoextraction of heavy metals in soil are realized. However, mechanisms of heavy metal accumulation and hyperaccumulation for cleanup of contaminated soils need more consideration. The problem of hyperaccumulator plants consists of their low biomass and slow growth. So, different ways to improve heavy metal phytoremediation should be considered. Bacteria play an important role in soil-plant interaction and their influence on heavy metal contamination attracted attention. Plant-assisted bioremediation involves remediation of contaminated soils with both plants and microorganisms associated to their rhizosphere. Alfalfa with its symbiotic bacteria was successfully applied to the final step of remediation of organically polluted areas. But the mechanisms and the role of bacteria in heavy metal accumulation by plants need further research. We present our results concerning the role of bacterial polysaccharides in metal accumulation by plants. It is shown that metal transfer into solution from elemental form depends on the exopolysaccharide (EPS) concentration in solution and glucuronic acid content in EPS. Bacterial polysaccharides do influence zinc uptake by the hyperaccumulator plant Thlaspi caerulescens. Possible perspectives for plant-bacterial remediation systems are discussed.