Genome-resolved metatranscriptomic analysis of arsenic demethylation and detoxification in a methanogenic rice paddy soil

In methanogenic rice paddy soil incubations, arsenic demethylation is linked to methanogen activity, with trimethylamine accelerating demethylation and associating rates with methylotrophic methyltransferase transcription.

• Why it matters: Arsenic methylation/demethylation in rice paddies shapes arsenic speciation and toxicity, yet the microbial pathways and how toxicity feedbacks regulate demethylation remain unclear.
• What they did: Genome-resolved metatranscriptomics was paired with arsenic speciation analysis in incubations using dimethylarsinic (DMAs) and the methanogenesis inhibitor 2-bromoethanesulfonate, while trimethylamine was added to test pathway links and transcriptional associations.
• The result: Methanosarcina metagenome assembled genomes dominated methyltransferase transcription and concurrently transcribed genes for multiple (methyl)arsenic oxidation and efflux pathways; higher DMAs inhibited methanogenesis and lowered pseudo first-order demethylation rate constants.

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