Unravelling biogeochemical drivers of methylmercury production in an Arctic fen soil and a bog soil

Zhang, Lijie; Philben, Michael; Taş, Neslihan; Johs, Alexander; Yang, Ziming; Wullschleger, Stan D.; Graham, David E.; Pierce, Eric M.; Gu, Baohua

doi:10.1016/j.envpol.2022.118878

Cited by 11 publications

(6 citation statements)

References 81 publications

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“…57,58 Therefore, the lack of MeHg formation in microcosms with N 2 O may be attributed to the inhibition of SRB, although the data cannot rule out the involvement of other microbial guilds [e.g., Fe(III)-reducing bacteria, methanogens]. 57,59 Fe(III) reduction was reported in these Arctic tundra soils, 9 and the observation of abundant Fe(III)-reducing bacteria (e.g., Geobacter) (Figure 4B) suggests Fe(III) reduction activity in the microcosms. N 2 O showed pronounced and immediate inhibition on CH 4 production in the Arctic soil microcosms (Figure 2B), consistent with previous studies reporting that N 2 O impacts methanogenesis.…”

Section: ■ Discussionmentioning

confidence: 99%

“…The result is consistent with prior studies that established SRB as the dominant players in Hg(II) methylation in Arctic soils and freshwater sediments when sulfate is available. 57 , 58 Therefore, the lack of MeHg formation in microcosms with N 2 O may be attributed to the inhibition of SRB, although the data cannot rule out the involvement of other microbial guilds [e.g., Fe(III)-reducing bacteria, methanogens]. 57 , 59 Fe(III) reduction was reported in these Arctic tundra soils, 9 and the observation of abundant Fe(III)-reducing bacteria (e.g., Geobacter ) ( Figure 4 B) suggests Fe(III) reduction activity in the microcosms.…”

Section: Discussionmentioning

confidence: 99%

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Inhibition of Methylmercury and Methane Formation by Nitrous Oxide in Arctic Tundra Soil Microcosms

Zhang

Yin

Sun

et al. 2023

Environ. Sci. Technol.

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Climate warming causes permafrost thaw predicted to increase toxic methylmercury (MeHg) and greenhouse gas [i.e., methane (CH 4 ), carbon dioxide (CO 2 ), and nitrous oxide (N 2 O)] formation. A microcosm incubation study with Arctic tundra soil over 145 days demonstrates that N 2 O at 0.1 and 1 mM markedly inhibited microbial MeHg formation, methanogenesis, and sulfate reduction, while it slightly promoted CO 2 production. Microbial community analyses indicate that N 2 O decreased the relative abundances of methanogenic archaea and microbial clades implicated in sulfate reduction and MeHg formation. Following depletion of N 2 O, both MeHg formation and sulfate reduction rapidly resumed, whereas CH 4 production remained low, suggesting that N 2 O affected susceptible microbial guilds differently. MeHg formation strongly coincided with sulfate reduction, supporting prior reports linking sulfate-reducing bacteria to MeHg formation in the Arctic soil. This research highlights complex biogeochemical interactions in governing MeHg and CH 4 formation and lays the foundation for future mechanistic studies for improved predictive understanding of MeHg and greenhouse gas fluxes from thawing permafrost ecosystems.

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Section: ■ Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Inhibition of Methylmercury and Methane Formation by Nitrous Oxide in Arctic Tundra Soil Microcosms

Zhang

Yin

Sun

et al. 2023

Environ. Sci. Technol.

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“…We constructed a HRG database by (1) extracting HRGs from BacMet version 2.0 [ 28 ] and (2) obtaining hgcAB gene sequences used by microorganisms to methylate Hg from previous studies [ 9 , 29 , 30 , 31 ]. First, utilizing an in-house Perl script, we used the keyword “Mercury” to search the “Compound” column of the BacMet2 gene annotation mapping file, to obtain the HRG GenBank IDs, which we used to extract the HRG sequences of the predicted HRGs in BacMet2.…”

Section: Methodsmentioning

confidence: 99%

“…First, utilizing an in-house Perl script, we used the keyword “Mercury” to search the “Compound” column of the BacMet2 gene annotation mapping file, to obtain the HRG GenBank IDs, which we used to extract the HRG sequences of the predicted HRGs in BacMet2. Second, the accession numbers or locus tags of the hgcAB genes from previous studies [ 9 , 29 , 30 , 31 ] were used to extract the hgcAB sequences from the NCBI protein database.…”

Section: Methodsmentioning

confidence: 99%

“…Stringent criteria (e-value ≤ 1e-5; identity ≥ 80%; coverage ≥ 90%) [ 33 , 34 ] were used in each case, except for hgcAB , for which a lenient criterion (e-value ≤ 1e-5) that was used due to few similarities. Homologous hgcA sequences without the conserved sequence motif [G(I/V)NVWC(A/S/G)(A/S/G)GK] and the homologous hgcB sequences that were not near hgcA in the genomes were discarded [ 30 , 35 ].…”

Section: Methodsmentioning

confidence: 99%

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Plasmid Genomes Reveal the Distribution, Abundance, and Organization of Mercury-Related Genes and Their Co-Distribution with Antibiotic Resistant Genes in Gammaproteobacteria

Yang

Zhang

et al. 2022

Genes

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Mercury (Hg) pollution poses human health and environmental risks worldwide, as it can have toxic effects and causes selective pressure that facilitates the spread of antibiotic resistant genes (ARGs) among microbes. More and more studies have revealed that numerous Hg-related genes (HRGs) can help to resist and transform Hg. In the present study, we systematically analyzed the HRG distribution, abundance, organization, and their co-distribution with ARGs, using 18,731 publicly available plasmid genomes isolated from a Gammaproteobacteria host. Our results revealed that there were many Hg-resistant (mer) operon genes but they were not extensively distributed across plasmids, with only 9.20% of plasmids harboring HRGs. Additionally, no hgcAB genes (which methylate Hg to create methylmercury) were identified in any of the analyzed plasmids. The host source significantly influenced the number of HRGs harbored by plasmids; plasmids isolated from humans and animals harbored a significantly smaller number of HRGs than plasmids isolated from the wastewater and sludge. HRG clusters displayed an extremely high organizational diversity (88 HRG cluster types), though incidences of more than half of the HRG cluster types was <5. This indicates the frequent rearrangement among HRGs in plasmids. The 1368 plasmids harboring both HRGs and ARGs, were dominated by Klebsiella, followed by Escherichia, Salmonella, and Enterobacter. The tightness of the HRG and ARG co-distribution in plasmids was affected by the host sources but not by pathogenicity. HRGs were more likely to co-occur with specific ARG classes (sulfonamide, macrolide-lincosamide-streptogramin, and aminoglycoside resistance genes). Collectively, our results reveal the distribution characteristics of HRGs in plasmids, and they have important implications for further understanding the environmental risks caused by the spread of ARGs through the plasmid-mediated co-transfer of ARGs and HRGs.

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Adsorption and intracellular uptake of mercuric mercury and methylmercury by methanotrophs and methylating bacteria

Zhang

Kang-Yun

Xia

et al. 2023

Environmental Pollution

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Unravelling biogeochemical drivers of methylmercury production in an Arctic fen soil and a bog soil

Cited by 11 publications

References 81 publications

Inhibition of Methylmercury and Methane Formation by Nitrous Oxide in Arctic Tundra Soil Microcosms

Inhibition of Methylmercury and Methane Formation by Nitrous Oxide in Arctic Tundra Soil Microcosms

Plasmid Genomes Reveal the Distribution, Abundance, and Organization of Mercury-Related Genes and Their Co-Distribution with Antibiotic Resistant Genes in Gammaproteobacteria

Adsorption and intracellular uptake of mercuric mercury and methylmercury by methanotrophs and methylating bacteria

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