Microbes vs. Neurotoxic methylmercury in farmlands and rice

 By: Ebie Rodriguez

The figure shows A and B graphical summaries of the microbial degradation of CH3Hg+concentration and the efficiency in C and D (Zhou et al. 2025).

Methylmercury is a neurotoxin produced from microbial conversion of inorganic mercury in rice paddy soils, which can accumulate in rice grains. Paddy and upland rotations are common in cropping systems that contribute CH3Hg+ to both soil types. This study aims to provide experimental evidence of the specific microbial taxa responsible for active CH3Hg+ degradation within the natural environment. The soil samples were collected from two agricultural regions known for Hg+ hotspots in Wanshan, Southwest China. The extent of degradation depended on the soil types, the initial background Hg levels, and ^13C enrichment to identify microbes involved in ^13C enrichment. After 28 days of incubation, the soils of high Hg-contaminated sites, paddy soil, High-P, and upland soil, High-Up, were calculated to have degradation efficiencies of CH3Hg+ were 86% and 37%, respectively, as illustrated in the figure above. The degradation efficiencies in the paddy soil (Low-P) and upland soil (Low-U) CH3Hg+ were 40% and 64%, respectively, as illustrated in the figure above. After using the 16S rRNA genes to determine the microorganisms degrading the ^13CH3Hg+, Xanthomonadaceae, Xanthobacteraceae, and Comamonadaceae were dominant families enriched in the ^13CH3Hg+ treatment in both High-P and Low-U soils. Overall, this study demonstrates the significant role of soil microorganisms in reducing the CH3Hg+ exposure risk to humans and wildlife.  

Original article:

Zhou X-Q, Chen K-H, Yu R-Q, Yang M, Liu Q, Hao Y-Y, Li J, Liu H-W, Feng J, Tan W, et al. 2025. Microbial potential to mitigate neurotoxic methylmercury accumulation in farmlands and rice. Nature 
Communications. 16(1). doi:http://doi.org/10.1038/s41467-025-60458-1. [accessed 2025 Sep 26]. https://www.nature.com/articles/s41467-025-60458-1#Fig1.