The Bioadsorption of Cadmium and Lead by Bacteria in Root Exudates Culture

Microorganisms are important for phytoremediation of soil contaminated with heavy metals. In the present study, bacteria Bacillus sp., Pseudomonas sp., Alcaligenes sp., and Flavobacterium sp. isolated from the Zhangshi Irrigation Area were applied to bioadsorbed Cd and Pb in liquid cultures with root exudates of sunflower as a sole carbon source. The experimental data demonstrated that these bacteria had a high potential of enrichment of Cd and Pb, and Bacillus sp. and Alcaligenes sp. had better ability to accumulate Cd or Pb than the others; the distinct bioadsorption of Cd and Pb by bacteria might depend on the physiology of bacteria, categories of heavy metals, and environmental factors (such as pH). In addition, root exudates of sunflower could not only support the growth of these bacteria, but also influence the toxicity and bioavailability of Cd and Pb. Our results indicated that amendment with bacteria isolated from heavy-metal-polluted soil and root exudates could be considered as a potential approach to enhance the phytoremediation of Cd- or Pb-contaminated soil.