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

Abstract

Anaerobic oxidation of methane (AOM) facilitates 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.