An origin for arsenobetaine involving bacterial formation of an arsenic?carbon bond

RITCHIE, A

doi:10.1016/j.femsle.2004.04.016

Cited by 13 publications

(22 citation statements)

References 14 publications

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“…29 This nucleoside then undergoes glycosidation to produce a 95 range of arsenosugars. 15,29 These arsenosugars are thought to subsequently be converted to AB along a pathway involving either arsenocholine (AC) or dimethylarsinoylacetate (DMAA) 12 (Fig. 2, b).…”

Section: Discussionmentioning

confidence: 99%

“…[8][9][10] However, less is known about the occurrence and behaviour of As in terrestrial organisms such as earthworms. 11 Until recently the organo-arsenic species AB was thought to be restricted to the marine environment, 12 but has now been demonstrated in terrestrial fungi 13 and 65 earthworms. 2,11,14 The biotransformation pathway for the formation of AB in marine organisms is thought to involve the carbohydrate containing As compounds known as arsenosugars.…”

Section: Introductionmentioning

confidence: 99%

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Arsenic biotransformation in earthworms from contaminated soils

et al. 2009

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Two species of arsenic (As) resistant earthworm, Lumbricus rubellus and Dendrodrillus rubidus, their host soils and soil excretions (casts) were collected from 23 locations at a former As mine in 5 Devon, UK. Total As concentrations, measured by ICP-MS, ranged from 255 to 13,080 mg kg -1 in soils, 11 to 877 mg kg -1 in earthworms and 284 to 4221 mg kg -1 in earthworm casts from a subsample of 10 of the 23 investigated sites. The samples were also measured for As speciation using HPLC-ICP-MS to investigate potential As biotransformation pathways. Inorganic arsenate (As V ) and arsenite (As III ) were the only species detected in the soil. As V and As III were also the dominant 10 species found in the earthworms and cast material together with lower proportions of the organic species methylarsonate (MA V ), dimethylarsinate (DMA V ), arsenobetaine (AB) and three arsenosugars. Whilst the inorganic As content of the earthworms increased with increasing As body burden, the concentration of organic species remained relatively constant. These results suggest that the biotransformation of inorganic arsenic to organic species does not contribute to As 15 resistance in the sampled earthworm populations. Quantification of As speciation in the soil, earthworms and cast material allows a more comprehensive pathway for the formation of AB in earthworms to be elucidated. Received (in XXX, IntroductionThe chemistry of As in environmental and biological systems is complex. Whilst inorganic As species are the most prevalent in abiotic environments, the uptake of inorganic As 25 by living organisms can lead to the synthesis of organic As species 1 through biotransformation. The ubiquitous, epegeic earthworm species L. rubellus and D. rubidus are known to inhabit soils highly contaminated with As at the former mine site of Devon Great Consols (DGC), UK. [2][3][4][5] These earthworms 30 are clearly resistant to As toxicity and several potential coping mechanisms have been proposed, yet the underlying mechanism behind this resistance is unknown. Behavioural adaptation, whereby the earthworm avoids contact with the contaminant, 4 is unlikely as earthworms from DGC are known 35 to have elevated As body burdens. 2,4, 5 The biotransformation of highly toxic inorganic As to the less toxic organic species arsenobetaine (AB) has been speculated as a mode of mitigating As toxicity in DGC earthworms. 2,4 An alternative mechanism involves the sequestration of arsenic in the 40 metallothionein-rich chloragogenous tissue which separates the intestine from the coelomic cavity. 3 With this mechanism it is proposed that inorganic As III binds to the sulphur-rich metallothionein thereby sequestering ingested As in a form that is not biologically reactive. The study of As speciation can provide important information on As biotransformation and toxicity and to date a multitude of organic As species have been identified. 7 The occurrence of organic As species and their biotransformation pathways are well documented in marine organisms such as crus...

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Arsenic biotransformation in earthworms from contaminated soils

et al. 2009

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“…Synthesis of arsenobetaine from a lyzed cell extract of Pseudomonas species suggests prokaryotes could produce trimethylarsonium compounds found in many marine organisms. [12] Arsenobetaine could be an osmolyte for marine organisms living in hyperosmotic environments. [13,14] Bacterial degradation of arsenobetaine to methylated arsenicals through formation of dimethylarsinoylacetate has been demonstrated in Paenibacillus and Pseudomonas species derived from Mytilus edulis, a marine mussel.…”

Section: Trimethylarsonium Compoundsmentioning

confidence: 99%

Commonalities in Metabolism of Arsenicals

Adair¹,

Waters²,

Devesa³

et al. 2005

Environ. Chem.

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Abstract. Elucidating the pathway of inorganic arsenic metabolism shows that some of methylated arsenicals formed as intermediates and products are reactive and toxic species. Hence, methylated arsenicals likely mediate at least some of the toxic and carcinogenic effects associated with exposure to arsenic. Trimethylarsonium compounds and arsenosugars are two other classes of arsenicals to which humans are routinely exposed and there is evidence that both classes are metabolized to produce methylated arsenicals. Here, we review evidence for production of methylated metabolism and consider the challenges posed in unraveling a complex web for metabolism of arsenicals in humans.

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“…Other reports (Khokiattiwong et al, 2001) showing the rapid degradation of AB by undefined mixed cultures of marine microorganisms (the involvement of bacteria was not proven in this case) with the formation of DMAA and subsequently DMA, did not involve the formation of TMAO as a product or intermediate. Most recently, we have reported on two bacterial isolates from the common marine mussel Mytilus edulis capable of degrading AB to DMA via DMAA (Jenkins et al, 2003) and the formation of AB from DMAA by a lysed-cell extract of one of these isolates (Ritchie et al, 2004). These studies indicate that two possible routes of bacterial degradation of AB exist, as shown in Figure 1.…”

Section: Introductionmentioning

confidence: 90%

“…Freshly collected human faeces (ca 1 g) were used to inoculate flasks containing 50 mL of mineral salt medium (Ritchie et al, 2004) and 2% yeast extract. Flasks were incubated with shaking at 37 C under aerobic or anaerobic conditions.…”

Section: Microcosmsmentioning

confidence: 99%

Biotransformation of arsenobetaine by microorganisms from the human gastrointestinal tract

Harrington

Brima

Jenkins

2008

Chemical Speciation & Bioavailability

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The consumption of fish and shellfish is a major route of human exposure to arsenic (As), because they contain relatively large concentrations of organoarsenicals, in particular arsenobetaine (AB). AB is considered non-toxic because of its rapid excretion from the human body. However, previous studies on human metabolism and excretion of AB have used the compound in solution rather than considering the effects that occur during the digestion of food in the gastrointestinal tract. In this preliminary study, we used microcosms inoculated with human faecal matter to investigate the aerobic and anaerobic degradation of AB by microorganisms associated with the large intestine. Samples were recovered over 30 days, centrifuged, filtered and the supernatant analysed for total As content and As speciation, using ICP -MS and HPLC -ICP -MS respectively. After 7 days the total As in the supernatants from the aerobic experiment fell to a minimum of 65% of the total added, recovering to 15% less than added after 30 days. By using anion and cation exchange chromatography coupled to ICP -MS detection, arsenobetaine (AB), dimethylarsinic acid (DMA), dimethylarsinoylacetic acid (DMAA) and trimethylarsine oxide (TMAO) were identified as degradation products. Results from the aerobic system showed that after 7 days incubation the AB had been degraded to DMA, DMAA and TMAO and after 30 days the degraded AB reappeared in the samples. The results for the anaerobic system showed no degradation of AB over the 30 day course of the experiment. These findings demonstrate for the first time that biocatalytic capability for AB degradation exists within the human gastrointestinal tract.

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An origin for arsenobetaine involving bacterial formation of an arsenic?carbon bond

Cited by 13 publications

References 14 publications

Arsenic biotransformation in earthworms from contaminated soils

Arsenic biotransformation in earthworms from contaminated soils

Commonalities in Metabolism of Arsenicals

Biotransformation of arsenobetaine by microorganisms from the human gastrointestinal tract

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