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Fungi Penicillium oxalicum SL2 was applied for Pb 2+ bioremediation in aqueous solution in this study. After 7 days of incubation at different initial concentrations of Pb 2+ (0, 100, 500 and 2500 mg L −1 ), most of Pb 2+ were removed (90, 98.3, and 86.2%), the maximum Pb content in mycelium reached about 155.6 mg g −1  dw. Meanwhile, the formation of extracellular secondary minerals and intracellular Pb-complex were observed and identified, the speciation of Pb in mycelium was also detected by X-ray absorption near-edge structure (XANES) spectroscopy, i.e., Pb-oxalate, Pb-citrate, Pb-hydrogen phosphate and Pb-glutathione analogues. In addition, content of glutathione and oxidized glutathione was increased under the exposure of Pb 2+ , which implied that glutathione might play a key role in Pb immobilization and detoxification in P. oxalicum SL2. This study elucidated partial mechanisms of Pb immobilization and speciation transformation of this strain, providing an alternative biomaterial in the bioremediation of Pb-contaminated wastewater. [ABSTRACT FROM AUTHOR]

The present study was conducted to determine the abilities of the living and nonliving Pseudomonas putida CZ1 cells, clays (goethite, kaolinite, smectite and manganite) and their composites to accumulate copper and zinc from a liquid medium, and elucidate the role of microbes on the mobility of heavy metals. Various mixtures of bacteria and clays were exposed to solutions of 0.025mM or 0.5mM Cu(II) and Zn(II) in 0.01M KNO3 to differentiate between so-called “high-affinity” sites and “low-affinity” sites. Clays associated in an edge-on orientation to the cells was observed by electron microscope (EM) examination of these metal-treated bacteria–clay aggregates. Adsorption experiments and desorption with 1.0M CH3COOK solution indicated that clays contain more high-affinity copper binding sites and less high-affinity zinc binding sites than that of bacteria, however, bacteria are involved in more low-affinity heavy-metal-binding sites. Carboxyl group activity is more important at weak-binding sites than at strong-binding sites. TEM-EDS analysis confirmed that most of Zn removed from solution was associated with P. putida CZ1 in the composites. These results suggest that bacteria play an important role in regulating the mobility of heavy metals in the soil environment. [Copyright &y& Elsevier]