| Abstract
| - The biomethylation of arsenic by the filamentous fungusScopulariopsis brevicaulis is well documented, andthe biomethylation of antimony by this fungus was recentlyestablished. However, in all the previous studies eachmetalloid was studied in isolation. Arsenic and antimonyare often associated in the environment, and so anunderstanding of interactions between these elements isnecessary. To this end, S. brevicaulis was grown in mediacontaining mixtures of arsenic and antimony compoundsin various proportions, and the principle nonvolatilebiomethylation products (trimethylantimony and trimethylarsenic species) in the medium were quantified by using HG-GC-AAS. It was found that the yield of trimethylantimonycompounds, obtained from the biomethylation of potassiumantimony tartrate, was increased in the presence ofsodium arsenite. The production of trimethylarsenic speciesfrom sodium arsenite was significantly inhibited in thepresence of antimony (either as potassium antimony tartrateor antimony trioxide) at antimony concentrations too lowto inhibit growth. This is although arsenic(III), in the absenceof antimony, is much more readily biomethylated. That is 1.2−5.3% of added arsenic is biomethylated by S. brevicauliswhereas only 0.0006−0.008% of added antimony(III) isbiomethylated over 1 month. Potassium hexahydroxyantimonate had no effect on arsenic biomethylation. The additionof potassium tartrate to cultures did not inhibit arsenicbiomethylation. The biomethylation of sodium arsenate wasnot inhibited as much by antimony compounds. Theinhibitory effect of antimony was found to be a functionof the ratio of antimony to arsenic rather than the absoluteamount of antimony.
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