The 5th International Conference of Geobiology

As a global pollutant, mercury (Hg) can be transformed into the more toxic methylmercury (MeHg) through biological processes in the environment. MeHg, a lipophilic neurotoxin, exhibits bioaccumulation and biomagnification effects, posing significant threats to ecosystems and human health. Subalpine peatlands serve as strong global sinks for Hg and are recognized as ‘hotspot’ areas for MeHg production. However, the microbial communities mediating Hg methylation and the geochemical factors influencing their distribution remain poorly understood. This study employed high-throughput sequencing of 16S rRNA and the Hg methylation gene hgcA to investigate the characteristics and controlling factors of Hg-methylating microbial communities in the subalpine peatland of Dajiuhu, located in Shennongjia, Hubei Province, China. The results revealed that the dominant Hg methylators in the Dajiuhu peatland were iron-reducing bacteria (FeRB; Geobacteraceae; 44.1%), followed by methanogens (Methanoregulaceae; 16.57%). Among these, FeRB exhibited the highest proportion of strains capable of Hg methylation (hgcA/qPCR = 6.52). Notably, although 16S rRNA analysis indicated that sulfate-reducing bacteria (SRB) were a dominant bacterial group in the Dajiuhu peatland (Syntrophaceae, Syntrophobacteraceae), the relative abundance (5.72%) and proportion of SRB strains with Hg methylation capability (hgcA/qPCR = 1.31) were comparatively low. Combined incubation experiments using specific inhibitors and accelerators revealed that rising MeHg levels triggered a compositional shift in Hg-methylating communities, transitioning from FeRB dominance to FeRB-methanogens co-dominance.The C/N ratio and redox potential (Eh) were identified as key geochemical factors influencing their community compositions. This study elucidates the composition and controlling factors of Hg-methylating microbial communities in subalpine peatland, providing critical insights for the prevention and control of MeHg pollution in wetland ecosystems.
 

peatland,Methylmercury,microbe