A significant 19th century public health problem was that the inhabitants of many houses containing wallpaper decorated with green arsenical pigments experienced illness and death. The problem was caused by certain fungi that grew in the presence of inorganic arsenic to form a toxic, garlic-odored gas. The garlic odor was actually put to use in a very delicate microbiological test for arsenic. In 1933, the gas was shown to be trimethylarsine. It was not until 1971 that arsenic methylation by bacteria was demonstrated. Further research in biomethylation has been facilitated by the development of delicate techniques for the determination of arsenic species. As described in this review, many microorganisms (bacteria, fungi, and yeasts) and animals are now known to biomethylate arsenic, forming both volatile (e.g., methylarsines) and nonvolatile (e.g., methylarsonic acid and dimethylarsinic acid) compounds. The enzymatic mechanisms for this biomethylation are discussed. The microbial conversion of sodium arsenate to trimethylarsine proceeds by alternate reduction and methylation steps, with S-adenosylmethionine as the usual methyl donor. Thiols have important roles in the reductions. In anaerobic bacteria, methylcobalamin may be the donor. The other metalloid elements of the periodic table group 15, antimony and bismuth, also undergo biomethylation to some extent. Trimethylstibine formation by microorganisms is now well established, but this process apparently does not occur in animals. Formation of trimethylbismuth by microorganisms has been reported in a few cases. Microbial methylation plays important roles in the biogeochemical cycling of these metalloid elements and possibly in their detoxification. The wheel has come full circle, and public health considerations are again important.

Microbial Methylation of Metalloids: Arsenic, Antimony, and Bismuth

The acute toxicity of arsenobetaine

Coordination chemistry of stibine and bismuthine ligands

The syntheses and properties of some alkylthioacetato and arylthioacetato derivatives of triphenylantimony(V) and -bismuth(V)

A series of Schiff base complexes of organoantimony(V) having formula R3SbL (R = phenyl or methyl, L = dibasic tetradentate ligands with the ONNO donor system) have been synthesised. The complexes are yellow to orange in colour. These complexes have been characterised by elemental analysis and i.r. and p.m.r. spectral data. Based on these measurements a pentagonal bipyramidal structure has been proposed for each one of these complexes.

Wilfred James Cecil Dyke

Papers

LXIII.—The interaction between alkyl Grignard reagents and antimony trichloride

CCLI.—Organic antimonial compounds. Part II

CCCXVII.—The interaction between alkyl Grignard reagents and arsenic trichloride