Interactions between Hg and soil microbes: microbial diversity and mechanisms, with an emphasis on fungal processes

Durand, Alexis; Maillard, François; Foulon, Julie; Chalot, Michel

doi:10.1007/s00253-020-10795-6

Cited by 17 publications

(3 citation statements)

References 146 publications

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“…Actually, Hg metabolic capacity is quite widespread among bacteria and archaea lineages (Christakis et al, 2021; Priyadarshanee et al, 2022), including bioaccumulation activity. Indeed, pure culture studies have documented significant bacterial uptake and accumulation of Hg (see Dranguet, Le Faucheur, Cosio, et al, 2017; Durand et al, 2020; Giovanella et al, 2017; Kiyono et al, 2003; Sayler et al, 1975; Zhang et al, 2020), with Hg bioaccumulation in some bacteria registering in the grams per liter range (Kis et al, 2017; Zhang et al, 2020). Further, controlled studies have shown that bacterial uptake of Hg can directly contribute to oyster Hg bioaccumulation (Sayler et al, 1975).…”

Section: Discussionmentioning

confidence: 99%

Arsenic and Mercury Distribution in an Aquatic Food Chain: Importance of Femtoplankton and Picoplankton Filtration Fractions

Alowaifeer

Clingenpeel

Kan

et al. 2022

Enviro Toxic and Chemistry

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Arsenic (As) and mercury (Hg) were examined in the Yellowstone Lake food chain, focusing on two lake locations separated by approximately 20 km and differing in lake floor hydrothermal vent activity. Sampling spanned from femtoplankton to the main fish species, Yellowstone cutthroat trout and the apex predator lake trout. Mercury bioaccumulated in muscle and liver of both trout species, biomagnifying with age, whereas As decreased in older fish, which indicates differential exposure routes for these metal(loid)s. Mercury and As concentrations were higher in all food chain filter fractions (0.1‐, 0.8‐, and 3.0‐μm filters) at the vent‐associated Inflated Plain site, illustrating the impact of localized hydrothermal inputs. Femtoplankton and picoplankton size biomass (0.1‐ and 0.8‐μm filters) accounted for 30%–70% of total Hg or As at both locations. By contrast, only approximately 4% of As and <1% of Hg were found in the 0.1‐μm filtrate, indicating that comparatively little As or Hg actually exists as an ionic form or intercalated with humic compounds, a frequent assumption in freshwaters and marine waters. Ribosomal RNA (18S) gene sequencing of DNA derived from the 0.1‐, 0.8‐, and 3.0‐μm filters showed significant eukaryote biomass in these fractions, providing a novel view of the femtoplankton and picoplankton size biomass, which assists in explaining why these fractions may contain such significant Hg and As. These results infer that femtoplankton and picoplankton metal(loid) loads represent aquatic food chain entry points that need to be accounted for and that are important for better understanding Hg and As biochemistry in aquatic systems. Environ Toxicol Chem 2023;42:225–241. © 2022 SETAC

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Section: Discussionmentioning

confidence: 99%

Arsenic and Mercury Distribution in an Aquatic Food Chain: Importance of Femtoplankton and Picoplankton Filtration Fractions

Alowaifeer

Clingenpeel

Kan

et al. 2022

Enviro Toxic and Chemistry

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“…The role of yeasts in Hg metabolism is poorly understood. A number of fungi, of which members of Yarrowia and Cryptococcus genus are among the best characterized, have been reported to tolerate Hg using different mechanisms, through their biosorption capacity, probably mediated by thiol groups on the surface of the cell, or through bioaccumulation via the sequestration of thiol-conjugated Hg to the vacuole (Brunker and Bott 1974;Wysocki and Tamás 2010), with the possible involvement of metallothioneins, phytochelatins, and other cysteine-rich proteins, as a means for SH groups to immobilize Hg in non-toxic form (Durand et al 2020). Sulfhydryl group-based immobilization is also the mechanism used by several high H 2 S producing isolates, which can co-precipitate Hg in non-toxic form as HgS (Aatif and Zakia 2011).…”

Section: Assessment Of Mercury Resistancementioning

confidence: 99%

Highly mercury-resistant strains from different Colombian Amazon ecosystems affected by artisanal gold mining activities

Cardona

Escobar

Acosta-González

et al. 2022

Appl Microbiol Biotechnol

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Two sites of the Colombian Amazon region with different levels of human intervention and mercury pollution were selected for the collection of samples of river and lake water, sediments, and associated forest soils. The Tarapacá region, affected mainly by barrage mining, showed low mercury concentrations, whilst in the Taraira region, affected by underground mining, there were several points with high mercury pollution levels. A collection of 72 bacterial and 10 yeast strains with different levels of mercury resistance was isolated and characterized. Most of the highly resistant bacterial strains (MIC > 40 mg L−1 HgCl2) were isolated from soil and sediment samples and belonged to either Pseudomonas (60%) or Bacillus (20%). Most of highly resistant bacterial strains were positive for the presence of the merA gene, suggesting an active mercury resistance mechanism. This was confirmed in the two most resistant strains, Pseudomonas sp. TP30 and Burkholderia contaminans TR100 (MIC = 64 and 71 mg L−1 HgCl2, respectively), which in the presence of increasing mercury concentrations expressed the merA gene at increasing levels, concomitant with a significant mercury reduction activity. Analysis of the MerA sequences present in the different isolates suggested a high gene conservation within the taxonomic groups but also several horizontal gene transfer events between taxonomically distant genera. We also observed a positive correspondence between the presence of the merA gene and the number of antibiotics to which the strains were resistant to. The most resistant strains are good candidates for future applications in the bioremediation of mercury-contaminated sites in the Amazon.Key points• Amazon sediments affected by underground gold mining have higher Hg levels.• Highly Hg-resistant isolates belonged to Pseudomonas and Bacillus genera.• TR100 and TP30 strains showed remediation potential to be used in the Amazon region. Graphical abstract

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“…A recent review stated that exposure to Hg is a threat to microbial soil functions involved in C and N cycles ( Durand et al, 2020 ). However, the majority of studies have been carried out shortly after Hg contamination (e.g., Frey and Rieder, 2013 ; Frossard et al, 2017 ).…”

Section: Introductionmentioning

confidence: 99%

Long-term mercury contamination does not affect the microbial gene potential for C and N cycling in soils but enhances detoxification gene abundance

Frey

Rast

et al. 2022

Front. Microbiol.

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Soil microorganisms are key transformers of mercury (Hg), a toxic and widespread pollutant. It remains uncertain, however, how long-term exposure to Hg affects crucial microbial functions, such as litter decomposition and nitrogen cycling. Here, we used a metagenomic approach to investigate the state of soil functions in an agricultural floodplain contaminated with Hg for more than 80 years. We sampled soils along a gradient of Hg contamination (high, moderate, low). Hg concentrations at the highly contaminated site (36 mg kg–1 dry soil on average) were approximately 10 times higher than at the moderately contaminated site (3 mg kg–1 dry soil) and more than 100 times higher than at the site with low contamination (0.25 mg kg–1 dry soil; corresponding to the natural background concentration in Switzerland). The analysis of the CAZy and NCyc databases showed that carbon and nitrogen cycling was not strongly affected with high Hg concentrations, although a significant change in the beta-diversity of the predicted genes was observed. The only functional classes from the CAZy database that were significantly positively overrepresented under higher Hg concentrations were genes involved in pectin degradation, and from the NCyc database dissimilatory nitrate reduction and N-fixation. When comparing between low and high Hg concentrations the genes of the EggNOG functional category of inorganic ion transport and metabolism, two genes encoding Hg transport proteins and one gene involved in heavy metal transport detoxification were among those that were highly significantly overrepresented. A look at genes specifically involved in detoxification of Hg species, such as the mer and hgc genes, showed a significant overrepresentation when Hg contamination was increased. Normalized counts of these genes revealed a dominant role for the phylum Proteobacteria. In particular, most counts for almost all mer genes were found in Betaproteobacteria. In contrast, hgc genes were most abundant in Desulfuromonadales. Overall, we conclude from this metagenomic analysis that long-term exposure to high Hg triggers shifts in the functional beta-diversity of the predicted microbial genes, but we do not see a dramatic change or breakdown in functional capabilities, but rather functional redundancy.

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Interactions between Hg and soil microbes: microbial diversity and mechanisms, with an emphasis on fungal processes

Cited by 17 publications

References 146 publications

Arsenic and Mercury Distribution in an Aquatic Food Chain: Importance of Femtoplankton and Picoplankton Filtration Fractions

Arsenic and Mercury Distribution in an Aquatic Food Chain: Importance of Femtoplankton and Picoplankton Filtration Fractions

Highly mercury-resistant strains from different Colombian Amazon ecosystems affected by artisanal gold mining activities

Long-term mercury contamination does not affect the microbial gene potential for C and N cycling in soils but enhances detoxification gene abundance

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