Concurrent methylation and demethylation of arsenic by fungi and their differential expression in the protoplasm proteome

- Transformation and migration change As toxicity and jeopardize human health.
- DMA(V) and inorganic As were detected in fungal cells after MMA(V) exposure.
- Concurrent methylation and demethylation of As was observed in fungal cells.
- Different As exposure triggers the differential expression of proteomic proteins.
- R7YMH0 donating a methyl group for SAM was up-regulated after MMA(V) exposure.

Microbial methylation and demethylation are central to arsenic's (As) biogeochemical cycling. Here, the transformations of monomethylarsonic acid (MMA(V)) (50 mg L−1) for 15 days in cells of As-methylating fungi, Fusarium oxysporum CZ-8F1, Penicillium janthinellum SM-12F4, and Trichoderma asperellum SM-12F1, were evaluated, and trace concentrations of As(III) and As(V) were observed in fungal cell extracts. Trace amounts of DMA(V) were also detected in MMA(V) and P. janthinellum SM-12F4 incubations. In situ X-ray absorption near edge structure (XANES) indicated that after exposure to MMA(V) (500 mg L−1) for 15 days, 28.6-48.6% of accumulated As in fungal cells was DMA(V), followed by 18.4-30.3% from As(V), 0-28.1% from As(III), and 4.8-28.9% from MMA(V). The concurrent methylation and demethylation of As occurs in fungal cells. Furthermore, a majority of proteins involved in metabolism, transport, ATP activity, biosynthesis, signal transduction, DNA activity, translation, and oxidative stress were upregulated in T. asperellum SM-12F1 cells after MMA(V) exposure compared to As(III), As(V), and DMA(V). The detoxification process of T. asperellum SM-12F1 was As species-specific. Methylenetetrahydrofolate reductase (R7YMH0) donation of a methyl group for S-adenosylmethionine (SAM) generation significantly increased following MMA(V) exposure.

203