Viral involvement in microbial anaerobic methane oxidation-mediated arsenic mobilization in paddy soil

Anaerobic oxidation of methane (AOM) facilitates arsenic (As) mobilization, posing a significant environmental risk. Soil viruses potentially participate in the microbial AOM process, yet their roles in methane-mediated As mobilization of paddy soil remain elusive. Here, an anaerobic microcosm study was conducted by inoculating microbial suspension with extracellular free virus and mitomycin C (MC)-induced virus, along with ¹³CH₄ injection. The results showed that extracellular free virus enhanced while MC-induced virus suppressed ¹³CH₄-mediated As mobilization. During the AOM process, both viruses inhibited ¹³CH₄ oxidation to ¹³CO₂. However, the extracellular free virus suppressed whereas the MC-induced virus enhanced ¹³CH₄ consumption, likely attributed to the viral influence on the ANME-2d abundance. The methane consumption differences were inferred to influence As reduction, as evidenced by a strong correlation between As(III) and ¹³CH₄ consumption concentrations. Moreover, virus-mediated methane assimilation into microbial biomass carbon influenced the overall microbial population. An increased abundance of Geobacter in the extracellular free virus treatment elevated net As(III) concentrations (up to 260 %) relative to treatment without virus in the presence of ¹³CH₄. In contrast, MC-induced virus led to a net 122 % reduction in As(III) concentration due to decreased Geobacter abundance. These findings provide new insights into soil viruses in microbial AOM-driven As mobilization, highlighting their crucial functions in soil ecosystems.