Selenium is an essential trace element for humans and many other organisms, but it can be toxic at higher doses
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
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:
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