Degradation of a tetramethylarsonium salt by microorganisms occurring in sediments and suspended substances under both aerobic and anaerobic conditions

Abstract

Microbial degradation of a tetramethylarsonium salt during incubation at 25 "C was investigated under both aerobic and anaerobic conditions. Two media (1/5 ZoBell 22163 and inorganic salt medium), added with the sediments or suspended substances as the sources of the microorganisms, were used. Degradation of the tetramethylarsonium salt occurred only in the ZoBell medium: under anaerobic conditions, trimethylarsine oxide and dimethylarsinic acid were derived with the sediments, and dimethylarsinic acid with the suspended substances, the salt degrading more rapidly with the former than with the latter. Small amounts of two metabolites, trimethylarsine oxide and inorganic arsenic(V), was also derived in the aerobically incubated ZoBell medium added with the suspended substances. This result means that the tetramethylarsonium salt is degraded to inorganic arsenic, which is the starting material for arsenic circulation in marine ecosystems, via trimethylarsine oxide and dimethylarsinic acid.

Review: Biological effects of organic arsenic compounds in seafood

“…18,19 TetMA may have originated in the marine sediments and was probably trapped in the external tissues of these marine animals, because this tetramethyl arsenic compound was detected in only a very few marine animals and/or marine sediments. 22,23 Interestingly, a recent study indicated that TetMA was formed in roasted seafood, although it was not detected at all before cooking. 24 As described above, in many countries, people are daily ingesting considerable amounts of arsenicals through the consumption of seafood; thus, it is necessary to investigate the effects of these organic arsenic compounds, including AsSug, AsCho, AsBe and TetMA, on living systems.…”

Demethylation of methylarsenic species by Mycobacterium neoaurum

“…5,6 The demethylation of the tetramethylarsonium ion, TMAO, DMA(V) and sodium methanearsonate by sediment microorganisms has also been reported. 7,8 In terms of isolated individual species of microorganisms, Challenger et al found that Penicillium notatum converts ClCH 2 CH 2 AsO(OH) 2 to trimethylarsine. 1 It is probable that this conversion occurs via cleavage of the arsenic-carbon bond of the ClCH 2 CH 2 -group and methylation.…”