Viruses enhance bacterial-mediated arsenic reduction processes by enriching rare functional taxa in flooded paddy soil

Abstract

Soil viruses are abundant and may play a role in arsenic (As) metabolic processes, which pose potential environmental risks in paddy field soils. However, little is known about the association of soil viruses with abundant and rare taxa and their ecological roles in regulating As transformation processes. Herein, we investigated the influence of soil viruses on bacterial-mediated As transformation and the response of abundant and rare taxa by inoculating with different soil viral concentrates (suspensions with no-viruses, extracellular free viruses, and mitomycin-C induced viruses) into sterilized soils containing a gradient of As concentrations. Results showed that both viral concentrates increased porewater As(III) concentrations, with extracellular free viruses increasing by 26.7% and 37.1% relative to treatment without viruses under low and high As conditions, while mitomycin-C induced viruses increased by 11.6% and 23.4%, respectively. Moreover, bacterial-generated As(III) displayed a significant positive correlation with Fe(II) concentrations even in the presence of viruses. Rare taxa were more susceptible than abundant taxa to virus inoculation. These changes in bacteria structure led to the enrichment of some rare functional taxa, especially those associated with potential Fe and As reduction functions. Evidence from qPCR analysis showed an increase in arsenic (arsC) and iron (FeRB) reduction genes, and these cumulative relative abundance of enriched rare functional taxa were significantly related to the increased As(III) concentrations. Overall, this study provides direct experimental evidence that viruses enrich rare functional taxa to enhance bacterial-mediated As reduction processes, highlighting a crucial role that viruses play in shaping soil ecosystem functions.