Mercury Methylation Capacity and Removal of Hg Species from Aqueous Medium by Cyanobacteria

Franco, Márcia R.; Mendes, Louise Aparecida; Windmöller, Cláudia Carvalhinho; Moura, Karen Ann Ferreira; Oliveira, Lucas Antônio Gomes; Barbosa, Francisco A. R.

doi:10.1007/s11270-018-3782-5

Cited by 23 publications

(6 citation statements)

References 41 publications

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“…Currently, there is very little support for phototrophs participating directly in Hg methylation. Aside from the initial research cited in our first review (Pongratz and Heumann 1998;Deng et al 2013), only one new study has emerged investigating the potential for direct methylation in the cyanobacterium Nostoc paludosum that showed no MeHg production (Franco et al 2018).…”

Section: Phototrophic Mercury Methylationmentioning

confidence: 99%

Shining light on recent advances in microbial mercury cycling

Grégoire

Poulain

2018

FACETS

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Mercury (Hg) is a global pollutant emitted primarily as gaseous Hg0 that is deposited in aquatic and terrestrial ecosystems following its oxidation to HgII. From that point, microbes play a key role in determining Hg’s fate in the environment by participating in sequestration, oxidation, reduction, and methylation reactions. A wide diversity of chemotrophic and phototrophic microbes occupying oxic and anoxic habitats are known to participate directly in Hg cycling. Over the last few years, new findings have come to light that have greatly improved our mechanistic understanding of microbe-mediated Hg cycling pathways in the environment. In this review, we summarize recent advances in microbially mediated Hg cycling and take the opportunity to compare the relatively well-studied chemotrophic pathways to poorly understood phototrophic pathways. We present how the use of genomic and analytical tools can be used to understand Hg transformations and the physiological context of recently discovered cometabolic Hg transformations supported in anaerobes and phototrophs. Finally, we propose a conceptual framework that emphasizes the role that phototrophs play in environmental Hg redox cycling and the importance of better characterizing such pathways in the face of the environmental changes currently underway.

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Section: Phototrophic Mercury Methylationmentioning

confidence: 99%

Shining light on recent advances in microbial mercury cycling

Grégoire

Poulain

2018

FACETS

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“…Studies investigating the role of primary producers on Hg methylation face the challenge of distinguishing their direct involvement as methylators from the indirect role they have in supplying nutrients to chemotrophic MeHg producers. − There is currently very little support, however, for phototrophs participating directly in Hg methylation . It is most likely that primary producers affect Hg II methylation by (i) providing a substrate that affects the activity of Hg methylating microbes, − (ii) releasing methylating compounds that would abiotically methylate Hg II (e .…”

Section: Introductionmentioning

confidence: 99%

“…13−15 There is currently very little support, however, for phototrophs participating directly in Hg methylation. 16 It is most likely that primary producers affect Hg II methylation by (i) providing a substrate that affects the activity of Hg methylating microbes, 17−19 (ii) releasing methylating compounds that would abiotically methylate Hg II (e.g., CH3Cl/Br/I or dimethylsulfoniopropionate), 20 and/or (iii) releasing chemical ligands that can affect the uptake of Hg II by methylators. 11 A necessary and rate limiting step in Hg methylation is the uptake of Hg to methylating microbes.…”

Section: ■ Introductionmentioning

confidence: 99%

Aerobic and Anaerobic Bacterial Mercury Uptake is Driven by Algal Organic Matter Composition and Molecular Weight

Mangal

Stenzler

Poulain

et al. 2018

Environ. Sci. Technol.

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The biological mobilization of mercury (Hg) into microbes capable of Hg methylation is one of the limiting steps in the formation of the neurotoxin methylmercury (MeHg). Although algal dissolved organic matter (DOM) has been associated with increased MeHg production, the relationship between bacterial Hg uptake and algal DOM remains unexplored. In this study, we aimed to address how the quantity and quality of DOM, freshly harvested from several algae, affected the bacterial uptake of Hg with the use of a biosensor capable of functioning both aerobically and anaerobically. We combined biosensor measurements with high-resolution mass spectrometry and field-flow fractionation to elucidate how DOM composition and molecular weight influenced microbial Hg uptake. We showed that freshly harvested DOM from Chlorophyte and Euglena mutabilis strongly inhibited aerobic and anaerobic Hg uptake, whereas DOM harvested from Euglena gracilis did not exhibit this same pronounced effect. Once fractionated, we found that amino acids and polyamines, most abundant in Euglena gracilis DOM, were positively correlated to increase Hg uptake, suggesting that these molecules are potentially underappreciated ligands affecting Hg bioavailability. As water quality is affected by eutrophication, algal community assemblages will change, leading to variations in the nature of autochthonous DOM released in aquatic systems. Our results highlight that variations in the emergent properties of DOM originating from varying algal species can have a profound effect on bacterial Hg uptake and thus methylation.

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“…Thus, the range of possible Hg-methylating communities could be very diverse. Some studies have highlighted the possibility of a mutualistic relationship between several species that promote Hg(II) methylation [ 80 , 82 ]. To this date, most studies on MeHg have focused on a small number of taxonomic groups, such as DSRB, DIRB, and some methanogens; however, there are growing concerns that some crucial taxa may have been overlooked [ 7 ].…”

Section: Discussionmentioning

confidence: 99%

The Influence of the Degree of Forest Management on Methylmercury and the Composition of Microbial Communities in the Sediments of Boreal Drainage Ditches

et al. 2022

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Inorganic mercury (Hg) can be methylated to the highly toxic and bioavailable methylmercury (MeHg) by microorganisms in anaerobic environments. The Hg methylation rate may be affected by forest management activities, which can influence the catchment soils, water, and sediments. Here, we investigate the influence of forest management in the form of ditch cleaning and beaver dam removal, as well as the seasonal variations, on sediment chemistry and microbiota. The relationships between MeHg concentrations in sediment samples and archaeal and bacterial communities assessed by 16S rRNA gene amplicon sequencing were investigated to determine the microbial conditions that facilitated the formation of MeHg. Concentrations of MeHg were highest in undisturbed catchments compared to disturbed or slightly disturbed sites. The undisturbed sites also had the highest microbial diversity, which may have facilitated the formation of MeHg. Low MeHg concentrations and microbial diversity were observed in disturbed sites, which may be due to the removal of organic sediment layers during ditch cleaning and beaver dam removal, resulting in more homogenous, mineral-rich environments with less microbial activity. MeHg concentrations were higher in summer and autumn compared to winter and spring, but the temporal variation in the composition and diversity of the microbial community was less than the spatial variation between sites. Beta diversity was more affected by the environment than alpha diversity. The MeHg concentrations in the sediment were positively correlated to several taxa, including Cyanobacteria, Proteobacteria, Desulfobacterota, Chloroflexi, and Bacteroidota, which could represent either Hg-methylating microbes or the growth substrates of Hg-methylating microbes.

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Mercury Methylation Capacity and Removal of Hg Species from Aqueous Medium by Cyanobacteria

Cited by 23 publications

References 41 publications

Shining light on recent advances in microbial mercury cycling

Shining light on recent advances in microbial mercury cycling

Aerobic and Anaerobic Bacterial Mercury Uptake is Driven by Algal Organic Matter Composition and Molecular Weight

The Influence of the Degree of Forest Management on Methylmercury and the Composition of Microbial Communities in the Sediments of Boreal Drainage Ditches

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