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Phytoremediation is a technology for extracting or inactivating pollutants. Echinochloa polystachya [(H. B. K. ) Hitchcock] (Poaceae) is a fast-growing perennial grass that is common in tropical areas and is often found in oil-polluted soils that contain high concentrations of heavy metals. However, its tolerance to heavy metals, and its ability to accumulate them, has yet to be investigated. Here we test the hypothesis that E. Polystachya is able to accumulate high concentrations of cadmium (Cd). Plants were grown hydroponically with different levels of Cd2+ (0, 0. 25, 1, 2, 10, 50, and 100mgL−1), and were found to be tolerant to Cd2+ at all levels. No metal-toxicity symptoms were observed at any Cd2+ level. Root and leaves Cd concentrations were 299±13. 93 and 233±8. 77mgkg−1 (on a dry weight basis), respectively. Scanning electron microscopy showed the inclusion of Cd within the xylem; this result was confirmed by energy dispersive X-ray spectrometry. Leaf tissues also accumulated Cd, especially within the bulliform cells of the epidermis. We conclude that E. Polystachya is a hyperaccumulator of Cd. While data for other metals are not yet available, E. Polystachya shows promise in the phytoextraction of Cd from polluted tropical sites. [Copyright &y& Elsevier]

A sulfate-reducing bacterium, was isolated from a 6 month trained enrichment culture in an anaerobic media containing phosphogypsum as a sulfate source, and, designated strain SA2. Cells of strain SA2 were rod-shaped, did not form spores and stained Gram-negative. Phylogenetic analysis of the 16S rRNA gene sequence of the isolate revealed that it was related to members of the genus Desulfomicrobium (average sequence similarity of 98%) with Desulfomicrobium baculatum being the most closely related (sequence similarity of 99%). Strain SA2 used thiosulfate, sulfate, sulfite and elemental sulfur as electron acceptors and produced sulfide. Strain SA2 reduced sulfate contained in 1–20g/L phosphogypsum to sulfide with reduction of sulfate contained in 2g/L phosphogypsum being the optimum concentration. Strain SA2 grew with metalloid, halogenated and non-metal ions present in phosphogypsum and with added high concentrations of heavy metals (125ppm Zn and 100ppm Ni, W, Li and Al). The relative order for the inhibitory metal concentrations, based on the IC50 values, was Cu, Te>Cd>Fe, Co, Mn>F, Se>Ni, Al, Li>Zn. [Copyright &y& Elsevier]