S57: Bacterial formation of nano-scaled materials from group 15 and 16 elements (Se, Te, and As).

Oxyanions of arsenic, selenium, and tellurium support the growth of anaerobes by acting as respiratory electron acceptors. The oxidation of carbon substrates (e.g., lactate) or inorganic electron donors (e.g., hydrogen or sulfide) results in the biochemical reduction of these oxyanions. For Group 16 elements, nano-sized minerals of Se(0) and Te(0) that form on the surfaces of these microbes and slough off into the surrounding medium have unusual opto-electrical properties (Oremland et al., 2004; Baesman et al., 2007; 2009). If an excess of electron donor is provided, a further dissimilatory reduction of Se(0) to selenide [Se(-II)] can be achieved by certain bacteria (Herbel et al., 2003; Baesman et al., 2009), although this has not been demonstrated for Te. In other anaerobes like Veillonella atypica, a direct reduction of selenite to selenide is possible (Pearce et al, 2009). Selenide can be reacted with metal cations to form nanoparticles of CdSe or ZnSe, which along with arsenic-sulfide nano-minerals may have commercial applications (e.g., photovoltaic cells). In the case of Te(0), a reverse property of optical limitation has been described (Liao et al., 2010).

Herbel, M.J. et al. 2003. Geomicrobiol. J. 20: 587 – 60.2

Oremland, R.S. et al. 2004. Appl. Environ. Microbiol. 70: 52 - 60.

Baesman, S.M. et al. 2007. Appl. Environ. Microbiol. 73: 2135 – 2143

Baesman, S.M. et al. 2009. Extremophiles 13: 695 – 705.

Pearce, C.I.  et al. 2009. Environ. Technol. 30: 1313 - 1326.

Liao, KS et al. 2010. Chem. Phys. Lett. 484: 242 - 246.