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華中農業大學資源與環境學院劉玉榮教授團隊對水稻土中微生物群落對MeHg的降解的作用進行了研究。相關成果發表於Environmental Science & Technology（IF=7.149）。
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Abstract
Bioaccumulation of the neurotoxin methylmercury (MeHg) in rice has raised worldwide concerns because of its risks to human health. Certain microorganisms are able to degrade MeHg in pure cultures, but the roles and diversities of the microbial communities in MeHg degradation in rice paddy soils are unknown. Using a series of microcosms, we investigated MeHg degradation in paddy soils from Hunan, Guizhou, and Hubei provinces, representing three major rice production regions in China, and further characterized one of the soils from the Hunan Province for microbial communities associated with MeHg degradation. Microbial demethylation was observed in all three soils, demonstrated by significantly more MeHg degraded in the unsterilized soils than in the sterilized controls. More demethylation occurred in water-saturated soils than in unsaturated soils, but the addition of molybdate and bromoethanesulfonic acid as the respective inhibitors of sulfate reducing bacteria and methanogens showed insignificant effects on MeHg degradation. However, the addition of Cu enhanced MeHg degradation and the enrichment of Xanthomonadaceae in the unsaturated soil. 16S rRNA Illumina sequencing and metatranscriptomic analyses of the Hunan soil consistently revealed that Catenulisporaceae, Frankiaceae, Mycobacteriaceae, and Thermomonosporaceae were among the most likely microbial taxa in influencing MeHg degradation in the paddy soil, and they were confirmed by combined analyses of the co-occurrence network, random forest modeling, and linear discriminant analysis of the effect size. Our results shed additional light onto the roles of microbial communities in MeHg degradation in paddy soils and its subsequent bioaccumulation in rice grains.
神經毒素甲基汞（MeHg）在水稻中的生物積累會對人類健康構成風險，引起了全世界的關注。某些微生物在純培養中能夠降解甲基汞，但水稻土中微生物群落在降解甲基汞過程中的作用及其多樣性尚不清楚。本文利用一系列微觀模型研究了中國三大代表性水稻產區湖南省、貴州省和湖北省的水稻土中MeHg的降解情況，並進一步對湖南省的一種土壤中與MeHg降解相關的微生物群落特性進行了研究。在所有三種土壤中都觀察到微生物去甲基化，未滅菌土壤中MeHg的降解明顯高於滅菌對照土壤。水飽和土壤中的去甲基化現象比不飽和土壤中的更明顯，但分別添加鉬酸鹽和溴乙烷磺酸作為硫酸鹽還原細菌和產甲烷菌的抑制劑對MeHg的降解影響不顯著。而Cu的加入促進了不飽和土壤中MeHg的降解和黃單胞菌科的富集。16S rRNA Illumina測序和環境轉錄組學分析湖南土壤均顯示，Catenulisporaceae、弗蘭克氏菌科、分枝桿菌科和高溫單孢菌科是最有可能影響水稻土中MeHg降解的微生物類群，共現網絡、隨機森林模型和效應量線性判別分析的綜合分析也證實了這一點。本研究結果進一步揭示了微生物群落對MeHg在水稻土中的降解及在水稻籽粒中的生物積累中的作用機制。
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