Mercury methylation and sulfate reduction rates in mangrove sediments, Rio de Janeiro, Brazil: The role of different microorganism consortia

Correia, Raquel Rose Silva; Guimarães, Jean Rémy Davée

doi:10.1016/j.chemosphere.2016.09.153

Cited by 42 publications

(12 citation statements)

References 34 publications

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“…Although our study was prompted by increased concerns surrounding MeHg accumulation in rice paddies, our findings could apply to other habitats that support steep redox gradients, competition for nutrients and cometabolic Hg transformations. Nutrient cycling and cometabolic Hg transformations stand to be closely linked in Hg methylation hotspots such as periphytic microbial mats (Olsen, Brandt, & Brooks, ), aquatic sediments (Correia & Guimarães, ; Fleming, Mack, Green, & Nelson, ) and waterlogged soils (Eklof et al, ). While our study makes a case for sulphur cycling as a coupling point for competing cometabolic Hg transformations, other nutrients such as iron (Bravo et al, ; Fleming et al, ; Sugio et al, ; Wiatrowski et al, ) and organic carbon (Christensen et al, ; Grégoire et al, ; Grégoire & Poulain, ) that are known to control Hg methylation and reduction have the potential to fulfil a similar role.…”

Section: Resultsmentioning

confidence: 99%

Reduced sulphur sources favour Hg^II reduction during anoxygenic photosynthesis by Heliobacteria

et al. 2019

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The consumption of rice has become a global food safety issue because rice paddies support the production of high levels of the potent neurotoxin, methylmercury. The production of methylmercury is carried out by chemotrophic anaerobes that rely on a diversity of terminal electron acceptors, namely sulphate. Sulphur can be a limiting nutrient in rice paddies, and sulphate amendments are often used to stimulate crop production, which can increase methylmercury production. Mercury (Hg) redox cycling can affect Hg methylation by controlling the delivery of inorganic Hg substrates to methylators in anoxic habitats. Whereas sulphur is recognized as a key substrate controlling methylmercury production, the controls sulphur exerts on other microbe‐mediated Hg transformations remain poorly understood. To explore the potential coupling between sulphur assimilation and anaerobic HgII reduction to Hg0, we studied Heliobacillus mobilis, a mesophilic anoxygenic phototroph representative from the Heliobacteriacea family originally isolated from a rice paddy. Here, we tested whether the redox state of the sulphur sources available to H. mobilis would affect its ability to reduce HgII. By comparing Hg0 production over a redox gradient of sulphur sources, we demonstrate that phototrophic HgII reduction is favoured in the presence of reduced sulphur sources such as thiosulphate and cysteine. We also show that cysteine exerts dynamic control on Hg cycling by affecting not only Hg's bioavailability but also its abiotic photoreduction under low light conditions. Specifically, in the absence of cells we show that organic matter (as yeast extract) and cysteine are both required for photoreduction to occur. This study offers insights into how one of the most primitive forms of photosynthesis affects Hg redox transformations and frames Heliobacteria as key players in Hg cycling within paddy soils, forming a basis for management strategies to mitigate Hg accumulation in rice.

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Section: Resultsmentioning

confidence: 99%

Reduced sulphur sources favour Hg^II reduction during anoxygenic photosynthesis by Heliobacteria

et al. 2019

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“…The Hg levels in sediments could also vary depending on the exposure of mudflats to tidal washing and vegetation cover, which emphasizes the role of mangrove roots in trapping sediments, leaf litter as well as Hg (Correia and Guimarães, 2016;Le et al, 2017). In the present study, the non-significant differences of [Hg] between riverbank and inside forest sediments for the majority of sites could be linked to the presence of homogenous vegetation, with small differences of canopy cover, and root presence from fringe line to the forest (10−15 m) inside.…”

Section: Sedimentsmentioning

confidence: 99%

“…In this context, Hg could partially be released back into atmosphere or converted into organic forms (e.g. methylmercury-MeHg) by microbes in the anoxic mangrove sediment enriched with dissolved organic matter (Correia and Guimarães, 2016).The Hg forms ultimately enter the food web through a trophic pathway, and in this case the molluscs being considered as primary consumers showed elevated Hg levels. Mercury can also be exported to adjacent habitats by physical factors such as tidal regimes and river flow (Bergamaschi et al, 2012) or trophic relay by migratory species (Hammerschmidt and Fitzgerald, 2006).…”

Section: Mercury Pathway In Matangmentioning

confidence: 99%

Distribution of mercury in sediments, plant and animal tissues in Matang Mangrove Forest Reserve, Malaysia

Wolswijk

Satyanarayana

et al. 2020

Journal of Hazardous Materials

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Charcoal production activities at the Matang Mangrove Forest Reserve (MMFR) in Peninsular Malaysia have a potential to emit volatile compounds such as Hg back into the ambient environment, raising concerns on the public health and safety. The present study was aimed at analyzing Hg concentration from different plant/ animal tissues and sediment samples (in total 786 samples) to understand clearly the Hg distribution at the MMFR. Leaves of Rhizophora spp. showed higher Hg concentration with an increasing trend from young, to mature, to senescent and decomposing stages, which was possibly due to accumulation of Hg over time. The low Hg concentration in Rhizophora roots and bark suggests a limited absorption from the sediments and a meagre accumulation/partitioning by the plant tissue, respectively. In the case of mangrove cockles the concentration of Hg was lower than the permissible limits for seafood consumption. Although the mangrove gastropod-Cassidula aurisfelis Bruguière had rather elevated Hg in the muscle tissue, it is still less than the environmental safely limit.

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“…The Hg-methylation by iron-reducing bacteria (IRB) was also evidenced (Fleming et al, 2006). Experiments conducted in mangrove sediments suggested that SRB activity could not explain all MeHg formation, this implies the direct or indirect participation of other microorganisms as IRB and methanogens and a complex relationship among these groups (Correia and Guimarães, 2017). Hg 2+ methylation by abiotic processes is also reported (Siciliano et al, 2005;Weber, 1993).…”

Section: Introductionmentioning

confidence: 99%

Production of methylmercury by sulphate-reducing bacteria in sediments from the orbetello lagoon in presence of high macroalgal loads

Pepi

Leonzio

Focardi

et al. 2020

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Methylmercury is a potent neurotoxin affecting shallow-water ecosystems. Mercury polluted sediment samples were collected at six different sites in the Orbetello Lagoon (central Italy) characterized by high levels of silt, iron, manganese hydroxides, and organic matter originated the latter originated from the decomposition of macroalgae. Porous water pointed out the presence of sulphates, methylmercury, and sulphides. Slurries arranged in anaerobic conditions from sediment aliquots from the six sites, with the addition of ionic mercury, highlighted the production of methylmercury. Sulphate reducing bacteria (SRB) were quantified in lagoon sediments; furthermore, sediments cultured under anaerobic conditions showed SRBs active in mercury methylation. Anaerobic cultures of SRB, amended with ionic mercury, produced methylmercury during the growth of bacterial cells. The percentage of aerobic mercury resistant bacteria was pointed out at each sampling site, evidencing the presence of bioavailable mercury. Several aerobic mercury resistant bacteria were isolated and their level of resistance to inorganic and organic forms of mercury was evaluated. These isolates may be potentially used for eventual bioremediation processes. Mercury methylation by SRB in the Orbetello Lagoon sediments was described for the first time, focusing the attention on the need for possible bioremediation processes by using autochthonous mercury resistant bacteria. Moreover, the influence of algal biomass on mercury methylation was highlighted for the first time in this lagoon ecosystem. The importance of removing algal biomass, as it represents a source of organic matter favouring the process of mercury methylation, was strongly pointed out in this study.

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Mercury methylation and sulfate reduction rates in mangrove sediments, Rio de Janeiro, Brazil: The role of different microorganism consortia

Cited by 42 publications

References 34 publications

Reduced sulphur sources favour Hg^II reduction during anoxygenic photosynthesis by Heliobacteria

Reduced sulphur sources favour Hg^II reduction during anoxygenic photosynthesis by Heliobacteria

Distribution of mercury in sediments, plant and animal tissues in Matang Mangrove Forest Reserve, Malaysia

Production of methylmercury by sulphate-reducing bacteria in sediments from the orbetello lagoon in presence of high macroalgal loads

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Mercury methylation and sulfate reduction rates in mangrove sediments, Rio de Janeiro, Brazil: The role of different microorganism consortia

Cited by 42 publications

References 34 publications

Reduced sulphur sources favour HgII reduction during anoxygenic photosynthesis by Heliobacteria

Reduced sulphur sources favour HgII reduction during anoxygenic photosynthesis by Heliobacteria

Distribution of mercury in sediments, plant and animal tissues in Matang Mangrove Forest Reserve, Malaysia

Production of methylmercury by sulphate-reducing bacteria in sediments from the orbetello lagoon in presence of high macroalgal loads

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Reduced sulphur sources favour Hg^II reduction during anoxygenic photosynthesis by Heliobacteria

Reduced sulphur sources favour Hg^II reduction during anoxygenic photosynthesis by Heliobacteria