33 D.M. Whitacre (ed.), Reviews of Environmental Contamination and Toxicology, Reviews of Environmental Contamination and Toxicology 223, DOI 10.1007/978-1-4614-5577-6_2, © Springer Science+Business Media New York 2013 1 Introduction Rapid industrialization and modernization around the world have produced the unfortunate consequence of releasing toxic wastes to the environment. Metal pollut- ants are derived mainly from industrial and agricultural activities. The former includes activities such as waste disposal, chemical manufacturing, and metal pol- lutants from vehicle exhaust, and the latter involves activities such as the use of agrochemicals, long-term application of sewage sludge, and wastewater to agricul- tural soils. Such releases have adversely affected human health and have produced toxic effects on plants and the soil microorganisms associated with them. Toxic metal contaminants from wastes or other products accumulate in the agricultural H.I. Tak • F. Ahmad • O.O. Babalola (*) Department of Biological Sciences, Faculty of Agriculture, Science and Technology, North-West University, Mafikeng Campus, Private Bag X2046, Mmabatho 2735, South Africa e-mail: olubukola.babalola@nwu.ac.za Advances in the Application of Plant Growth-Promoting Rhizobacteria in Phytoremediation of Heavy Metals Hamid Iqbal Tak, Faheem Ahmad, and Olubukola Oluranti Babalola Contents 1 Introduction .......................................................................................................................... 33 2 Phytoremediation ................................................................................................................. 36 2.1 Biological Availability of Metals in Soil ..................................................................... 37 2.2 Plant Uptake and Transport of Metals ......................................................................... 38 2.3 Plant Mechanisms for Metal Detoxification................................................................ 39 3 Plant Growth-Promoting Bacteria ........................................................................................ 40 3.1 How Do PGPR Combat Heavy-Metal Stress? ............................................................ 42 3.2 Synergistic Interaction of PGPR and Plants in Heavy-Metal Remediation ................ 43 3.3 ACC Deaminase and Plant Stress Reduction from Ethylene ...................................... 44 4 Summary .............................................................................................................................. 46 References .................................................................................................................................. 47