PNNL

Abstract

Soil viruses are abundant, but the influence of the environment and climate on soil viruses remains poorly understood. Here, we addressed this gap by comparing the diversity, abundance, lifestyle and metabolic potential of DNA viruses in three grassland soils with historical differences in average annual precipitation: low in Eastern Washington (WA), high in Iowa (IA) and intermediate in Kansas (KS). Bioinformatics analyses were applied to identify a total of 2,631 viral contigs including 14 complete viral genomes from three deep metagenomes (1 terabase (Tb) each) that were sequenced from bulk soil DNA. An additional three replicate metagenomes (~0.5 Tb each) were obtained from each location for statistical comparisons. Identified viruses were primarily bacteriophages targeting dominant bacterial taxa. Both viral and host diversity were higher in soil with lower precipitation. Viral abundance was also significantly higher in the arid WA location, compared to IA and KS. More lysogenic markers and fewer CRISPR spacer hits were found in WA, reflecting more lysogeny in historically drier soil. More putative auxiliary metabolic genes (AMGs) were also detected in WA compared to the historically wetter locations. The AMGs occurring in 18 pathways could potentially contribute to carbon metabolism and energy acquisition in their hosts. Structural equation modeling (SEM) suggested that historical precipitation influenced viral lifecycle and selection of AMGs. The observed and predicted relationships between soil viruses and various biotic and abiotic variables have value for predicting viral responses to environmental change.