Preprints
https://doi.org/10.5194/egusphere-2024-590
https://doi.org/10.5194/egusphere-2024-590
12 Jun 2024
 | 12 Jun 2024
Status: this preprint is open for discussion.

Dissolved organic matter fosters core mercury-methylating microbiome for methylmercury production in paddy soils

Qiang Pu, Bo Meng, Jen-How Huang, Kun Zhang, Jiang Liu, Yurong Liu, Mahmoud A. Abdelhafiz, and Xinbin Feng

Abstract. Methylmercury (MeHg), accumulated in rice grain, is highly toxic for human. Its production is largely driven by microbial methylation in paddy soils; however, dissolved organic matter (DOM) represents a hotspot for soil biogeochemistry, resulting in MeHg production, remain poorly understood. Here, we conducted hgcA gene sequencing and genome-resolved metagenomic analysis to identify core Hg-methylating microbiome and investigate the effect of DOM on core Hg-methylating microbiome in paddy soils across a Hg contamination gradient. In general, the Hg-methylating microbial communities varied largely with the degree of Hg contamination in soils. Surprisingly, a core Hg-methylating microbiome was identified exclusively associated with MeHg concentration. The partial Mantel test revealed strong linkages among core Hg-methylating microbiome composition, DOM and MeHg concentration. Structural equation model further indicated that core Hg-methylating microbiome composition significantly impacted soil MeHg concentration (accounting for 89 %); while DOM was crucial in determining core Hg-methylating microbiome composition (65 %). These results suggested that DOM regulates MeHg production by altering the composition of core Hg-methylating microbiome. The presence of various genes associated with carbon metabolism in the metagenome-assembled genome of core Hg-methylating microorganisms suggests that different DOMs stimulate the activity of core Hg-methylating microorganisms to methylate Hg, which was confirmed by pure incubation experiment with Geobacter sulfurreducens PCA (core Hg-methylating microorganism) amended with natural DOM solution extracted from investigated soils. Overall, DOM simultaneously changes core Hg-methylating microbiome composition and functional activity and thus enhances MeHg production in paddy soils.

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Qiang Pu, Bo Meng, Jen-How Huang, Kun Zhang, Jiang Liu, Yurong Liu, Mahmoud A. Abdelhafiz, and Xinbin Feng

Status: open (until 24 Jul 2024)

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  • RC1: 'Comment on egusphere-2024-590', Emi Stuart, 16 Jul 2024 reply
Qiang Pu, Bo Meng, Jen-How Huang, Kun Zhang, Jiang Liu, Yurong Liu, Mahmoud A. Abdelhafiz, and Xinbin Feng
Qiang Pu, Bo Meng, Jen-How Huang, Kun Zhang, Jiang Liu, Yurong Liu, Mahmoud A. Abdelhafiz, and Xinbin Feng

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Short summary
This study examines the effect of dissolved organic matter (DOM) on microbial mercury (Hg) methylation in paddy soils. It uncovers that DOM regulates Hg methylation mainly through altering core Hg-methylating microbiome composition and boosting the growth of core Hg-methylating microorganisms. The study highlights that in the regulation of methylmercury formation in paddy soils, more attention should be paid to changes in DOM concentration and composition.