Selenium is an essential trace element for humans and many other organisms, but it can be toxic at higher doses (ToxFAQs: Selenium). Selenium is required for incorporation into selenocysteine, which is the 21st amino acid identified in ribosomal-mediated peptide synthesis (reviewed by Allmang and Krol, 2006). Selenoproteins have been described in animals (including humans), bacteria and archaea, and the green alga Chlamydomonas reinhardtii (Novoselov et al., 2002), but not in higher plants or fungi (Allmang and Krol, 2006). However, some yeast and filamentous fungi will incorporate selenium into amino acids non-specifically in place of sulfur when grown in selenium-enriched media (Haas and Velten, 1992; Ramadan and Razak, 1988).

Bacteria that can respire selenate and selenite, and subsequently reduce the selenium oxyanions to elemental selenium has been described (reviewed by Stoltz and Ormeland, 1999). Bacteria have been reported to methylate selenate, selenite, and selenocysteine to yield dimethyl selenide and dimethyl diselenide (reviewed by Stoltz et al., 2006).

For more information:

Search Medline for selenium metabolism AND bacteria

Kashiwa M, Ike M, Mihara H, Esaki N, Fujita M. Removal of soluble selenium by a selenate-reducing bacterium Bacillus sp. SF-1. Biofactors. 2001;14(1-4):261-5.

Rother M, Resch A, Wilting R, Bock A. Selenoprotein synthesis in archaea. Biofactors. 2001;14(1-4)75-83.

Turner RJ, Weiner JH, Taylor DE. Selenium metabolism in Eschericia coli. Biometals. 1998 Sep;11(3):101-25.