Biology subjects

Emerson, J. B.

Publications and source records attributed to Emerson, J. B..

At least 19 recordsLinked to original sources

bioRxiv2026

Burn intensity regulates post-fire effects on soil N2O emissions: A grassland soil pyrocosm study

Post-fire soil emissions of nitric oxide (NO) and nitrous oxide (N2O) are important ecosystem nitrogen (N) loss pathways, but their flux dynamics vary widely across studies, making generalizations challenging. Natural variation in burn intensity--or heat energy released during combustionm--may help resolve this variability by mediating the soil physicochemical and biological drivers of these emissions. Here, we used an experimental "pyrocosm" system to evaluate how varying burn intensity influences post-fire NO and N2O emissions using soil from a Southern California grassland across 18 weeks. Over several months, we measured soil NO and N2O fluxes alongside soil pH, extractable nitrate (NO3-) and ammonium (NH4+), net NH4+ production, net nitrification, soil carbon (C) pools, microbial biomass C, and the potential activities of five extracellular hydrolytic enzymes under Control, Low- (100.1 {+/-} 20.0 oC peak soil temperature at 5 cm depth), and High-intensity (243.8 {+/-} 7.4 oC peak soil temperature at 5 cm depth) burns. Soil NO emissions were not significantly affected by burn intensity. In contrast, N2O emissions tripled under low burn intensity relative to unburned controls, but did not differ from controls at high burn intensity. This stimulation of N2O emission under low burn intensity was driven by increased denitrification, as supported by elevated soil pH and labile C availability, and an 88% reduction in net nitrification that signaled active NO3- consumption. Under high burn intensity, however, severe loss of microbial biomass, soil C, and NO3- constrained denitrification, with rising hydrolytic enzyme activities over time suggesting C limitation. Together, these findings demonstrate that post-fire N2O emissions reflect a fire intensity-dependent balance between microbial mortality and resource limitation, helping to explain divergent N emissions across ecosystems.

ecology↗

bioRxiv2026

PEONY: a global reference database of DNA viral (vOTU) sequences from viral size-fractionated metagenomes (viromes)

We present an update to the PIGEON (Phages and Integrated Genomes Encapsidated or Not) reference database of DNA viral sequences (vOTUs, mostly dsDNA bacteriophages) from global ecosystems. To reflect the inclusion of only virus size-fractionated metagenome- (virome-)derived vOTUs, we reintroduce the database as PEONY (Phages Encapsidated ONlY) and present new data summarizing the utility of this database.

microbiology↗

bioRxiv2026

ZipStrain Enables Rapid and Precise Strain-Resolved Metagenomics

Strain-resolved metagenomics characterizes microbial communities at nucleotide-level resolution, enabling researchers to differentiate identical from closely related organisms and characterize population structure and gene content variation. Here we introduce ZipStrain, a program that performs highly accurate strain-resolved metagenomics over 500x faster than available methods while offering superior RAM management. Applied to a dataset of 2,754 samples spanning human populations, we identify a strain-sharing gradient across social relationships, reveal striking variation in clonal structure across bacteria and bacteriophage, and pinpoint genes whose nucleotide identity deviates from genome-wide expectations. ZipStrain is distributed as an open-source Python package and accompanying Nextflow pipeline at https://github.com/OlmLab/ZipStrain.

bioinformatics↗

bioRxiv2026

Divergent successional patterns and infection dynamics in virion and transcriptionally active soil viral communities following phosphorus amendment and wet-up

Viruses are key regulators of terrestrial carbon, nitrogen, and phosphorus cycling, yet how environmental perturbations structure viral activity remains poorly resolved. Rewetting of seasonally dry soils triggers rapid microbial and viral responses, but the relationships between virion-associated and transcriptionally active viral communities, and the role of phosphorus in these dynamics, remain unclear. Here, we integrated viromics, metatranscriptomics, environmental DNA (eDNA), and amplicon sequencing to track viral succession and virus-host interactions over three weeks following soil rewetting, with and without phosphorus amendment. We identified 13,840 viral populations (vOTUs), of which 3,803 were transcriptionally active, representing ongoing infections. Wet-up significantly altered virion and transcriptionally active viral communities, while phosphorus selectively influenced prokaryotic and transcriptionally active viral communities but not virion composition. Virus-host linkages were predicted for 32% of vOTUs, with transcriptionally active bacteriophages infecting Actinomycetota increasing under phosphorus amendment. Following wet-up, virion abundance decreased [~]3-fold while virocells increased [~]5-fold, indicating a shift from viral persistence in dry soils to active infection. Phosphorus further enhanced virocell abundance. eDNA captured rapid viral turnover and revealed transient dynamics not resolved by viromes or metatranscriptomes alone. Together, these results demonstrate that soil viral communities are structured by distinct but complementary molecular pools that operate over different ecological timescales. Wet-up activates a reservoir of persistent virions, while phosphorus availability regulates infection dynamics and host-virus coupling. These findings highlight viruses as dynamic drivers of microbial turnover and nutrient cycling following environmental perturbation, advancing a more predictive understanding of soil ecosystem responses to changing resource availability.

ecology↗

bioRxiv2026

Host community activity, but not always composition, explains viral biogeography in bulk and rhizosphere soils over a tomato growing season

The soil microbiome is key to plant health and nutrient acquisition, and viruses likely play important but largely unknown roles in these processes. To interrogate bulk and rhizosphere soil viral biogeography, we collected samples over a tomato growing season in California from an experiment testing arbuscular mycorrhizal fungi (AMF) treatment. We generated 78 viromes, 16S rRNA gene, and ITS1 amplicon datasets, and 33 rhizosphere metatranscriptomes. Of 67,038 DNA viral species genomes (vOTUs), 25% were previously identified, predominantely in agricultural systems, suggesting habitat filtering and greater viral homogeneity across agricultural compared to natural soils globally. Rhizospheres had significantly higher DNA viral richness than bulk soils, whereas no significant richness differences were observed for other biota. 60% of vOTUs were shared between compartments, compared to only 21-23% of bacterial and fungal taxa. Although bulk soil viral biogeography resembled that of prokaryotes, with significant structuring by moisture content, greater virome similarity between high-moisture bulk soils and rhizospheres suggests that conditions with high host activity selected for similar viral communities. In rhizospheres, while bacterial and fungal communities differed most over time, DNA and RNA viral communities differed most by sampling location, matching prokaryotic transcriptional patterns and further implicating host activity in viral biogeography. Similarly, AMF treatment induced changes in the prokaryotic transcriptome but, across biota, only significantly affected DNA viral communities. Overall, results indicate strong viral responses to spatiotemporally localized conditions, with viral biogeography reflecting both dispersal opportunities (high between neighboring bulk and rhizosphere soils, low across fields) and selection via local host activity.

genomics↗

bioRxiv2025

Spatial and depth structuring predominate over temporal variation in Mediterranean grassland soil viral communities

Viruses have the potential to influence microbial community structure and elemental cycling in soils, but it remains unclear how these communities are distributed across space and time, which can shape how they respond to environmental change and impact ecosystem processes. Mediterranean grasslands, with their pronounced seasonal moisture fluctuations, offer an ideal system to examine viral biogeography. While previous studies hint at spatial structuring and moisture controls on viral communities, temporal responses to seasonal moisture shifts have not been comprehensively investigated in situ. Here, we generated 59 viromes and leveraged 89 metagenomes from two Mediterranean grasslands to measure soil viral communities across horizontal space (sampling zone), depth, and key seasonal stages of the Mediterranean water year (e.g. plant productivity, dry down and wetup). Sampling zone was the dominant driver of viral community composition in viromes, with time secondarily explaining variation in viral communities. In contrast, viral richness and DNA yields varied primarily across time. Spatial structuring also emerged in viruses recovered from metagenomes, with depth having the strongest effect, followed by sampling zone. Environmental variables and predicted host distributions partially explained these patterns, but substantial variation remained unaccounted for, suggesting a role for dispersal limitation. Overall, soil viral communities were primarily structured by spatial factors, with temporal and environmental influences acting secondarily, highlighting the importance of fine-scale spatial dynamics in understanding viral ecology. Future studies should explicitly examine the role of dispersal limitation and fine-scale host-environment interactions to fully resolve drivers of soil viral biogeography.

ecology↗

bioRxiv2025

DNA extraction and virome processing methods strongly influence recovered human gut viral community characteristics

Accurately characterising the human gut virome is critical to understanding virus-microbiome-host interactions. However, widely used methods introduce biases that complicate data interpretation and limit cross-study comparability. For instance, multiple-displacement amplification (MDA) preferentially amplifies single-stranded DNA viruses, while total metagenomes are dominated by non-viral sequences, reducing viral signal. These traditional methods have not been systematically compared to viral size-fraction metagenomes (viromes) prepared without MDA. To address this, we applied four common methods for characterising human gut viral community composition (total metagenomes, viromes with/ without DNase treatment (to remove free DNA), and MDA viromes) to a human stool sample, with technical triplicates for each approach. MDA biased viral community composition to a shocking degree: Microviridae formed [~]90% of MDA viromes compared to just 2% of non-MDA viromes. Removing ssDNA viruses from data analyses substantially reduced, but did not eliminate, MDA bias. Metagenomes were enriched for putative temperate phages and predicted Bacillota-phages, whereas predicted Bacteroidetes-phages dominated all viromes, suggesting that metagenomes and viromes select for different populations within the total viral community. DNase treatment had little-to-no effect on virome richness or community composition. This proof-of-principle experiment demonstrates that preparatory methods for viral community analysis can lead to substantially different conclusions from the same faecal sample, and we provide a comprehensive omic data analysis framework for comparing laboratory methodologies for viral ecology. With sufficient DNA yields now easily achievable from human gut viromes without the use of MDA, our results suggest that this biased amplification method should be avoided in human gut virome studies. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=112 SRC="FIGDIR/small/690293v1_ufig1.gif" ALT="Figure 1"> View larger version (35K): org.highwire.dtl.DTLVardef@36252org.highwire.dtl.DTLVardef@2c06f0org.highwire.dtl.DTLVardef@7b7cceorg.highwire.dtl.DTLVardef@13ec804_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical AbstractC_FLOATNO C_FIG

microbiology↗

bioRxiv2024

Soil viral and prokaryotic communities shifted significantly after wildfire in chaparral and woodland habitats

Increased wildfire activity warrants more research into fire-driven biotic changes in soil, given that soil microbes contribute to biogeochemical processes by way of organic matter decomposition, nutrient cycling, and promoting plant growth. Viruses of prokaryotes apply pressure to microbial communities, making their responses to fire also important for understanding post-fire ecology. Leveraging viromes and 16S rRNA gene amplicon sequencing, here we studied viral and prokaryotic community responses to wildfire in woodland and chaparral soils at five timepoints over one year following the California LNU Complex wildfire. We also compared post-fire samples to unburned controls at the final three timepoints, beginning five months after the fire. Viromic DNA yields were low-to-undetectable (indicative of low viral particle abundances), particularly for the first post-fire timepoint, and comparisons to controls suggest a return to baseline viral particle abundances within five months of the wildfire. Viral and prokaryotic community composition and soil chemistry differed significantly in burned samples compared to controls from both habitats. Compared to controls, a greater proportion of viral species (vOTUs) from a burned conifer forest were detected in both burned habitats here, suggesting fire-associated habitat filtering. Published viromes collected from the same sites nine months pre-fire were more similar to controls than to post-fire viromes. Together, these results indicate significant changes in soil viral and prokaryotic communities due to wildfire.

microbiology↗

bioRxiv2024

Locally heterogeneous soil viral and prokaryotic responses to prescribed burn correspond with patchy burn severity in a mixed conifer forest

Prescribed burning, a strategy to mitigate wildfires, imparts physicochemical and biological changes to soil. The effects of burns on soil viruses and virus-host dynamics are largely unexplored, despite known viral and prokaryotic contributions to biogeochemical processes. Using a viromic (<0.2 {micro}m size fraction metagenomic) approach, we assessed how viral communities responded to a spring prescribed burn in a mixed conifer forest and whether soil chemical properties and/or prokaryotic host communities could explain the observed patterns. From 120 soil samples (two per depth at 0-3 and 3-6 cm from four burned and two control plots at five timepoints, two before and three after the burn), 91 viromes and 115 16S rRNA gene amplicon libraries were sequenced. Plot location had the greatest effect on explaining variance in viral communities, over treatment (burned or not), depth, and timepoint. Viral and prokaryotic communities exhibited locally heterogenous responses to the fire, with some burned communities resembling unburned controls. This was attributed to patchy burn severity (defined by soil chemistry). Low viromic DNA yields indicated substantial loss of viral biomass in high-severity locations. The relative abundances of Firmicutes, Actinobacteria, and the viruses predicted to infect them significantly increased along the burn severity gradient, suggesting survival of spore formers and viral infection of these abundant, fire-responsive taxa. Our analyses highlight the importance of a nuanced view of soil community responses to fire, not just to burn overall, but to the specific degree of burn severity experienced by each patch of soil, which differed for nearby soils in the same fire.

ecology↗

bioRxiv2024

Virome responses to heating of a forest soil suggest that most dsDNA viral particles do not persist at 90°C

Many fundamental characteristics of soil viruses remain underexplored, including the effects of high temperatures on viruses and their hosts, as would be encountered under disturbances like wildland fire, prescribed burning, and soil solarization. In this study, we leveraged three data types (DNase-treated viromes, non-DNase-treated viromes, and 16S rRNA gene amplicon sequencing) to measure the responses of soil viral and prokaryotic communities to heating to 30{degrees}C, 60{degrees}C, or 90{degrees}C, in comparison to field and control conditions. We investigated (1) the response of dsDNA viral communities to heating of soils from two horizons (O and A) from the same forest soil profile, (2) the extent to which specific viral taxa could be identified as heat-sensitive or heat-tolerant across replicates and soil horizons, and (3) prokaryotic and virus-host dynamics in response to heating. We found that both viral and prokaryotic communities responded similarly to the treatment variables. Community composition differed most significantly by soil source (O or A horizon). Within both soil horizons, viral and prokaryotic communities clustered into three groups, based on beta-diversity patterns: the ambient community (field, control, and 30{degrees}C samples) and the 60{degrees}C and 90{degrees}C communities. As DNase-treated viromic DNA yields were below detection limits at 90{degrees}C, we infer that most viral capsids were compromised after the 90{degrees}C treatment, indicating a maximum temperature threshold between 60{degrees}C and 90{degrees}C for most viral particles in these soils. We also identified groups of heat-tolerant and heat-sensitive vOTUs across both soil sources. Overall, we found that over 70% of viral populations, like their prokaryotic counterparts, could withstand temperatures as high as 60{degrees}C, with shifts in relative abundance explaining most community compositional differences across heating treatments.

genomics↗

bioRxiv2023

Exploring viral particle, soil, and extraction buffer physicochemical characteristics and their impacts on extractable viral communities

Soil viruses are expected to be pivotal members of soil ecosystems, and recent advances in viral size fraction metagenomic (viromic) approaches have substantially improved our ability to interrogate soil viral ecology. However, the first step of viromics relies on extraction buffers to effectively remove viral particles from the soil matrix for downstream analysis, and viral extraction efficiency at this stage could be affected by the interplay between viral particles, soils, and extraction buffer chemistry. Here, we investigated whether extraction buffer chemistry affected extractable viral community composition measured by viromics from different soil types, for both biological (samples collected 1 meter apart) and technical (subsamples from the same soil homogenate) replicates. We first investigated protein-supplemented phosphate-buffered saline pH (PPBS, pHs 4.5, 5.5, 6.5, and 7.5) on a forest, grassland and wetland soil that exhibited different soil edaphic properties, and then we tested different buffer chemistries (PPBS, Carbonated Buffer, Glycine, and Saline Magnesium) on just the wetland soil. Spatial distance, or where the sample was taken in the field (i.e., biological replicate), was the primary driver of extractable viral community composition across all buffers and soils tested. Differences in viral community composition according to extraction buffer properties were only observed in the grassland technical replicates at PPBS buffer pH 4.5, as well as in both the wetland technical and biological replicates treated with different buffer chemistries, but the effects of buffer chemistry were secondary to spatial distance in all cases where spatial distance was a factor. The lack of buffering capacity in the grassland soil technical replicates likely increased sorption of some viral particles at pH 4.5, but neither protein composition nor isoelectric point (both calculated bioinformatically) explained this phenomenon. Given that most soil viral ecological studies to date include sample collection schemes over distances much farther apart than the 1-meter distances considered here, results suggest that extraction buffer chemistry is likely of much lower importance than ecological considerations, such as spatial distance, in the design of future soil viral ecological investigations. HIGHLIGHTSO_LISpatial distance was the main driver of extractable viral community composition. C_LIO_LIExtraction buffer chemistry secondarily structured wetland viral communities. C_LIO_LIAt pH 4.5, PPBS buffer likely increased viral sorption in homogenized grassland soil. C_LIO_LIIncreased sorption was not explained by estimated viral protein isoelectric points. C_LI

microbiology↗

bioRxiv2023

Almond rhizosphere viral, prokaryotic, and fungal communities differed significantly among four California orchards and in comparison to bulk soil communities

Characterization of rhizosphere microbiomes and their interactions is essential to a holistic understanding of plant health in support of sustainable agriculture. Viruses are a key, understudied component of rhizosphere microbiomes, with potential impacts on both plant-beneficial and -pathogenic organisms through infection. In this study, we sampled rhizospheres and bulk soils associated with 15 almond trees in four California orchards and generated viromic, 16S rRNA gene, and ITS1 amplicon sequencing datasets to compare viral, prokaryotic, and fungal communities. In total, 10,440 viral operational taxonomic units (vOTUs), 16,146 bacterial and archaeal OTUs, and 6,684 fungal OTUs were recovered. All three community types differed most significantly among the four orchards and secondarily between bulk and rhizosphere soils. Despite compositional differences, no significant differences in richness were observed between bulk and rhizosphere soils for any of the studied biota. Overall, viruses, prokaryotes, and fungi shared similar beta-diversity patterns in almond rhizospheres and bulk soils on a regional scale, counter to recently observed decoupling between viral and prokaryotic community biogeographic patterns in a variety of bulk soils.

ecology↗

bioRxiv2023

Soil viral communities differed by management and over time in organic and conventional tomato fields

Viruses are known contributors to biogeochemical cycling in diverse habitats, but viral community studies in soil are relatively rare. Although prior work has suggested spatial structuring as a primary driver of local soil viral community ecological patterns, here we show that agricultural management can significantly impact soil viral community composition. We generated 18 soil viromes and 24 total metagenomes from six plots, three under organic and three under conventional management in Davis, CA, USA. Despite the significant impact of management on viral community structure and soil physicochemistry, approximately 44% of the detected viral species (vOTUs) were present in soils from both management practices. These common vOTUs regularly comprised >65% of the viral community by relative abundance. Many (56%) of the vOTUs were detected both during the tomato growing season and post-harvest, indicating persistence through time. Together, these results indicate habitat-specific differences in viral community composition, yet relative stability and persistence of viral communities within agricultural soils, in contrast to their recently observed dynamics in natural soils.

microbiology↗

bioRxiv2023

Dispersal, habitat filtering, and eco-evolutionary dynamics as drivers of local and global wetland viral biogeography

Wetlands store 20-30% of the worlds soil carbon, and identifying the microbial controls on these carbon reserves is essential to predicting feedbacks to climate change. Although viral infections likely play important roles in wetland ecosystem dynamics, we lack a basic understanding of wetland viral ecology. Here 63 viral size-fraction metagenomes (viromes) and paired total metagenomes were generated from three time points in 2021 at seven fresh- and saltwater wetlands in the California Bodega Marine Reserve. We recovered 12,826 viral population genomic sequences (vOTUs), 4.4% of which were also detected at the same field site two years prior, indicating a small degree of population stability or recurrence. Viral communities differed most significantly across the seven wetland sites and were also structured by habitat (plant community composition and salinity). Read mapping to a new version of our reference database, PIGEONv2.0 (now with 515,763 vOTUs), revealed 196 vOTUs present over large geographic distances, often reflecting shared habitat characteristics. Wetland vOTU microdiversity was significantly lower locally than globally and lower within than between time points, indicating greater divergence with increasing spatiotemporal distance. Viruses tended to have broad predicted host ranges via CRISPR spacer linkages to metagenome-assembled genomes (whether this reflects true biology remains to be seen), and increased SNP frequencies in CRISPR-targeted major tail protein genes suggest viral eco-evolutionary dynamics, potentially in response to both immune targeting and to changes in host cell receptors involved in viral attachment. Together, these results highlight the importance of dispersal, environmental selection, and eco-evolutionary dynamics as drivers of local and global wetland viral biogeography.

ecology↗

bioRxiv2023

Viral but not bacterial community succession is characterized by extreme turnover shortly after rewetting dry soils

As central members of soil trophic networks, viruses have the potential to drive substantial microbial mortality and nutrient turnover. Pinpointing viral contributions to terrestrial ecosystem processes remains a challenge, as temporal dynamics are difficult to unravel in the spatially and physicochemically heterogeneous soil environment. In Mediterranean grasslands, the first rainfall after seasonal drought provides an ecosystem reset, triggering microbial activity during a tractable window for capturing short-term dynamics. Here, we simulated precipitation in microcosms from four distinct, dry grassland soils and generated 144 viromes and 84 metagenomes to characterize viral, prokaryotic, and relic DNA dynamics over 10 days. Vastly different viral communities in each soil followed remarkably similar successional trajectories. Wet-up triggered a significant increase in viral abundance and richness, followed by extensive compositional turnover. While temporal turnover in prokaryotic communities was much less pronounced, differences in the relative abundances of Actinobacteria (enriched in dry soils) and Proteobacteria (enriched in wetted soils) matched those of their predicted phages, indicating viral predation of dominant bacterial taxa. Rewetting also rapidly depleted relic DNA, which subsequently re-accumulated, indicating substantial new microbial mortality in the days after wet-up, particularly of the taxa putatively under phage predation. Production of abundant, diverse viral particles via microbial host cell lysis appears to be a conserved feature of the early response to soil rewetting, and results suggest the potential for Cull-the-Winner dynamics, whereby viruses infect and cull but do not decimate dominant host populations.

microbiology↗

bioRxiv2022

Substantial differences in soil viral community composition within and among four Northern California habitats

Viruses contribute to food web dynamics and nutrient cycles in diverse ecosystems, yet the biogeographical patterns that underlie these viral dynamics are poorly understood, particularly in soil. Here, we identified trends in soil viral community composition in relation to habitat, moisture content, and physical distance. We generated 30 soil viromes from four distinct habitats (wetlands, grasslands, woodlands, and chaparral) by selectively capturing virus-sized particles prior to DNA extraction, and we recovered 3,432 unique viral species (vOTUs). Viral communities differed significantly by soil moisture content, with viral richness generally higher in wet compared to dry soil habitats. However, vOTUs were rarely shared between samples, including replicates <10 m apart, suggesting that soil viruses may not disperse well and that future soil viral community sampling strategies may need to account for extreme community differences over small spatial scales. Of the 19% of vOTUs detected in more than one sample, 93% were from the same habitat and site, suggesting greater viral community similarity in closer proximity and under similar environmental conditions. Within-habitat differences indicate that extensive sampling would be required for rigorous cross-habitat comparisons, and results belie emerging paradigms of higher viral activity in wet soils and soil viral community spatial heterogeneity.

microbiology↗

bioRxiv2022

Spatial turnover of soil viral populations and genotypes overlain by cohesive responses to moisture in grasslands

Although soil viral abundance, diversity, and potential roles in microbial community dynamics and biogeochemical cycling are beginning to be appreciated1-5, little is known about the patterns and drivers of soil viral community composition that underlie their contributions to terrestrial ecology. Here, we analyzed 43 soil viromes from a precipitation manipulation experiment in a Mediterranean grassland in California, USA. We recovered 5,315 viral population sequences (vOTUs), and viral community composition exhibited a highly significant distance-decay relationship within the 18 m long field. This pattern was recapitulated in the microheterogeneity of 130 prevalent vOTUs (detected in >=90% of the viromes), which tended to exhibit significant negative correlations between genomic similarity of their predominant allelic variants and distance. Although spatial turnover was also observed in the bacterial and archaeal communities from the same soils, the signal was dampened relative to the viromes, suggesting differences in assembly drivers at local scales for viruses and their microbial hosts and/or differences in the temporal scales captured by viromes and total DNA. Despite the overwhelming spatial signal, vOTUs responsive to a decrease in soil moisture were significantly enriched in a predicted protein-sharing subnetwork of 326 vOTUs linked to 191 known actinobacteriophages, suggesting a genomically cohesive viral response to soil moisture evocative of environmental filtering, potentially by way of actinobacterial hosts. Overall, soil viral ecological processes appear to be highly constrained in space and tightly coupled to the heterogeneous, dynamic soil environment and thus fundamentally different from those of their well-mixed and more thoroughly studied marine counterparts.

microbiology↗

bioRxiv2021

RNA viral communities are structured by host plant phylogeny in oak and conifer leaves

Wild plants can suffer devastating diseases, experience asymptomatic, persistent infections, and serve as reservoirs for viruses of agricultural crops, yet we have a limited understanding of the natural plant virosphere. To access representatives of locally and globally distinct wild plants and investigate their viral diversity, we extracted and sequenced dsRNA from leaves from 16 healthy oak and conifer trees in the UC Davis Arboretum (Davis, California). From de novo assemblies, we recovered 389 RNA-dependent RNA polymerase (RdRp) gene sequences from 384 putative viral species, and a further 580 putative viral contigs were identified with virus prediction software followed by manual confirmation of virus annotation. Based on similarity to known viruses, most recovered viruses were predicted to infect plants or fungi, with the highest diversity and abundance observed in the Totiviridae and Mitoviridae families. Phyllosphere viral community composition differed significantly by host plant phylogeny, suggesting the potential for host-specific viromes. The phyllosphere viral community of one oak tree differed substantially from other oak viral communities and contained a greater proportion of putative mycoviral sequences, potentially due to the trees more advanced senescence at the time of sampling. These results suggest that oaks and conifers harbor a vast diversity of viruses with as-yet unknown roles in plant health and phyllosphere microbial ecology.

ecology↗