Geochemistry

Selenospheres

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Science  16 Jan 2004:
Vol. 303, Issue 5656, pp. 289
DOI: 10.1126/science.303.5656.289b

Selenium is an important biological trace element: an essential part of some metalloenzymes and a nutrient at low concentrations, but a pollutant and a toxic species at high levels. Elemental selenium is used in many electronics applications, and recent efforts have focused on growing microscopic selenium wires and crystals with advantageous characteristics and optical properties for use in devices. Oremland et al. show that phylogenetically distinct groups of bacteria that live in a range of environments process selenium in ways that may bear on these aspects of selenium chemistry. These bacteria reduce selenium oxyanions in order to grow and deposit elemental selenium externally. Imaging and spectroscopy show that the selenium is precipitated as uniform crystalline nanospheres about 300 nm in diameter. Surprisingly, different bacteria produce spheres with different arrangements of the selenium atoms and hence different optical properties. — BH

Appl. Environ. Microbiol. 70, 52 (2004).

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