Biomethylation of Arsenic, Antimony and Bismuth

Abstract

Biomethylation of metals or metalloids refers to the process whereby living organisms cause direct linkage of methyl groups to the metal(loid)s through enzymatic transfer of a preformed methyl group. The attachment of a methyl group to a metal(loid) changes the chemical and physical properties of the element, which in turn influences its mobility, geological cycling and toxicity. Biomethylation of the following metal(loid)s have been definitively established, although for most very little is known about the biological mechanism involved: Cd, Hg, Tl, Ge, Sn, Pb, As, Sb, Bi, Se and Te. The biological systems responsible for metal(loid) biomethylation are almost exclusively microorganisms. Anaerobic prokaryotes, operating in anoxic environments such as sediments from environmental waters and landfill sites, are major biocatalysts of metal(loid) biomethylation in the natural environment. Methylmetal(loid)s have also been shown to occur in soils from disparate locations and some aerobic and facultatively anaerobic bacteria, fungi and lower algae have been shown to be capable of metal(loid) biomethylation. Although higher organisms have not been shown to biomethylate true metals, methyl derivatives of some metalloids (including those of Se and As) are formed in a wide range of higher animals and plants.Over the past decade there has been a diversification of methods for the detection and measurement of organometallic compounds. Generally, this has been accompanied by improvements in reliability of detection and measurement of organometal(loid)s at low

Radioactive Semivolatiles in Nuclear Fuel Reprocessing

“…Trimethyl and triethyl antimony [Sb(CH 3 ) 3 and Sb(C 2 H 5 ) 3 ] are also gases at ambient conditions. Trimethly antimony is typically found at landfills and composts (Diaz-Bone et al 2011, Feldmann 2003, Filella 2010, Jenkins 2002, Jenkins 2011, Kosters et al 2003, Long and Sackman 1955. They do not react readily with water under aerobic and anaerobic conditions (Filella 2010, Jenkins 2002.…”

CHAPTER 17. Arsenic, Antimony and Bismuth

“…As a Group Vb element, bismuth forms pentavalent and trivalent salts but most Bi(V) compounds are appreciably less stable that Bi(III). 15,16 Bismuth is stable in oxygen and insoluble in water but dissolves in concentrated nitric acid to form bismuth nitrate; this slowly decomposes to bismuth subnitrate. Bismuth forms a range of inorganic salts, mainly with the Bi(III) valancy, all are insoluble in water and most have a low known toxicity threshold in mammalian systems.…”

Bioaccumulation and biovolatilization of various elements using filamentous fungus Scopulariopsis brevicaulis

“…It is assumed that chemical elements such as arsenic, selenium, tellurium or antimony cannot be significantly accumulated by microbial cells, but they can be effectively transformed, especially by biomethylation processes, to methylated or alkylated products, which are often volatile (Bentley and Chasteen ). Biomethylation of metals and metalloids is a natural phenomenon occurring in living organisms causing direct linkage of methyl groups to the metals or metalloids through enzymatic transfer of a methyl group (Fatoki ; Jenkins ). This methylation pathway is known as Challenger mechanism and refers to a series of metabolic reduction and oxidative methylation of metals and metalloids reactions resulting in the formation of methylated compounds (Challenger ; Cullen and Reimer ; Bentley and Chasteen ).…”