Review: Biological methylation of less‐studied elements

Thayer, John S.

doi:10.1002/aoc.375

Cited by 102 publications

(76 citation statements)

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“…However, our study indicates that substantial and variable losses of trace elements may take place in peat bogs due to methylation and subsequent volatilization. Such potential losses via methylation processes need to be carefully considered for all elements that undergo methylation (amongst others Hg, Pb, Sb, As and Se 44 ), and may present a limitation for the use of peat bogs as archives of atmospheric trace element deposition.…”

Section: Discussionmentioning

confidence: 99%

Natural wetland emissions of methylated trace elements

et al. 2014

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Natural wetlands are well known for their significant methane emissions. However, trace element emissions via biomethylation and subsequent volatilization from pristine wetlands are virtually unstudied, even though wetlands constitute large reservoirs for trace elements. Here we show that the average volatile fluxes of selenium (o0.12 mg m À 2 day À 1 ), sulphur (o37 mg m À 2 day À 1 ) and arsenic (o0.54 mg m À 2 day À 1 ) from a pristine peatland are considerable and consistent over two summers. We compare these fluxes with the total concentrations in the peat and show that selenium is up to 40 times more efficiently volatilized than arsenic, and over 100 times more efficiently volatilized than sulphur. We further show that the volatilization of selenium and arsenic increases with temperature, implying that emissions of these health-relevant trace elements will increase with global warming. We suggest that biomethylation and volatilization in wetlands play a crucial role in the mobilization and global biogeochemical cycling of trace elements.

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Section: Discussionmentioning

confidence: 99%

Natural wetland emissions of methylated trace elements

et al. 2014

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“…Two scenarios are plausible for bismuth methylation in the human body: a microbial pathway with participation of microorganisms present in the intestine and an endogenous pathway as described for arsenic and other elements (Thayer, 2002;Aposhian and Aposhian, 2006). Anaerobic incubation of feces samples obtained from volunteers after ingestion of bismuth showed that intestinal microorganisms are able to methylate bismuth ex vivo Michalke et al, 2007Michalke et al, , 2008.…”

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…In particular, alkylation often seems to considerably increase the toxic potential of metal(loid)s. Many studies have shown that in the environment methylated and also, in some cases, hydride species can be formed by different mechanisms and from a variety of metal(loid)s (Craig, 2003). In particular, microorganisms, e.g., bacteria and fungi, have been reported to be involved in this specific kind of conversion (Thayer, 2002).In contrast to the considerable knowledge that has accumulated on the interaction of microorganisms with metal(loid)s in the environment, a paucity of information is currently available on the respective processes inside the human body. This lack of knowledge is particularly striking in view of the fact that certain segments of the digestive tract, namely, the oral cavity and the colon, are colonized by myriads of bacteria.…”

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confidence: 99%

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Determination of Trimethylbismuth in the Human Body after Ingestion of Colloidal Bismuth Subcitrate

Boertz¹,

Hartmann²,

Sułkowski³

et al. 2008

Drug Metab Dispos

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ABSTRACT:Biological methylation and hydride formation of metals and metalloids are ubiquitous environmental processes that can lead to the formation of chemical species with significantly increased mobility and toxicity. Whereas much is known about the interaction of metal(loid)s with microorganisms in environmental settings, little information has been gathered on respective processes inside the human body as yet. Here, we studied the biotransformation and excretion of bismuth after ingestion of colloidal bismuth subcitrate (215 mg of bismuth) to 20 male human volunteers. Bismuth absorption in the stomach and upper intestine was very low, as evidenced by the small quantity of bismuth eliminated via the renal route. Total bismuth concentrations in blood increased rapidly in the first hour after ingestion. Most of the ingested bismuth was excreted via feces during the study period. Trace levels of the metabolite trimethylbismuth [(CH 3 ) 3 Bi] were detected via low temperaturegas chromatography/inductively coupled plasma-mass spectrometry in blood samples and in exhaled air samples. Concentrations were in the range of up to 2.50 pg/ml (blood) and 0.8 to 458 ng/m 3 (exhaled air), with high interindividual variation being observed. Elimination routes of bismuth were exhaled air (up to 0.03‰), urine (0.03-1.2%), and feces. The site of (CH 3 ) 3 Bi production could not be identified in the present study, but the intestinal microflora seems to be involved in this biotransformation if accompanying ex vivo studies are taken into consideration.It is a well known fact that the toxicity of metal(loid)s is essentially dependent on the chemical form, i.e., on the species of the element in question (Craig, 2003;Dopp et al., 2004; Hirner and Emons, 2004). In particular, alkylation often seems to considerably increase the toxic potential of metal(loid)s. Many studies have shown that in the environment methylated and also, in some cases, hydride species can be formed by different mechanisms and from a variety of metal(loid)s (Craig, 2003). In particular, microorganisms, e.g., bacteria and fungi, have been reported to be involved in this specific kind of conversion (Thayer, 2002).In contrast to the considerable knowledge that has accumulated on the interaction of microorganisms with metal(loid)s in the environment, a paucity of information is currently available on the respective processes inside the human body. This lack of knowledge is particularly striking in view of the fact that certain segments of the digestive tract, namely, the oral cavity and the colon, are colonized by myriads of bacteria. The difficulty of analyzing metal(loid) organic compounds at trace and even ultratrace levels might at least partly account for this information gap.After a pilot study with three volunteers , we performed an ingestion experiment with bismuth, administering this element as a single p.o. dose to 20 male volunteers in the form of a therapeutically used colloidal bismuth subcitrate compound. Bismuth was chosen as the element of interest ...

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“…Microorganisms have been shown to be capable of methylating a wide range of metals including Ge, Cd, In, Sn, Hg, Tl, Pb, Bi, and Po as well as metalloids, including As, Se, Sb, and Te [2]. Of these…”

Section: Introductionmentioning

confidence: 99%

Biotransformation of metal(loid)s by intestinal microorganisms

Diaz-Bone

Wiele

2010

Pure and Applied Chemistry

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Many metals and metalloids undergo complex biotransformation processes by micro organisms in the environment, namely, Ge, As, Se, Cd, In, Sn, Sb, Te, Hg, Tl, Pb, Bi, and Po. Though the human intestine harbors a highly diverse and metabolically active microbial community, the knowledge on metal(loid) biotransformation by gut microbiota is limited. Microbial metal(loid) metabolism in the gut is highly relevant when assessing health risks from oral exposure, as both the bioavailability and the toxicity of the ingested compound can be modulated. This review gathers and compares a broad selection of scientific studies on the intestinal biotransformation of metal(loid)s.It can be inferred that metal(loid) biotransformation by intestinal microbiota is a common process, resulting in both beneficial and adverse toxicological effects. Whereas for Hg the intestinal demethylation of methylmercury results in enhanced elimination, highly bioavailable and toxic arsenic and Bi species are formed by intestinal microorganisms. In either case, we conclude that the gut microbial potency should be considered to be taken up in toxicokinetic studies and models for assessing the health risks of oral metal(loid) exposure. This will allow the relevance of intestinal metal(loid) biotransformation to be assessed for human health risks.

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Review: Biological methylation of less‐studied elements

Cited by 102 publications

References 167 publications

Natural wetland emissions of methylated trace elements

Natural wetland emissions of methylated trace elements

Determination of Trimethylbismuth in the Human Body after Ingestion of Colloidal Bismuth Subcitrate

Biotransformation of metal(loid)s by intestinal microorganisms

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