Biology subjects

Sorensen, J. W.

Publications and source records attributed to Sorensen, J. W..

8 recordsLinked to original sources

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

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↗

bioRxiv2021

Soil viral communities are structured by pH at local and global scales

Viruses shape microbial community structures, impacting metabolic pathways and influencing biogeochemical cycles. Despite their importance, the influence of biotic and abiotic factors on viral community structures across environmental gradients in soil is relatively unknown compared to their prokaryotic hosts. While soil pH strongly influences microbial community structure, it is unclear whether there is a similar influence on soil virus communities. In this study, prokaryotic and viral communities were characterized in soils sampled from the extremes of a long-term pH-manipulated soil gradient (pH 4.5 and 7.5), and viral populations were compared to those in a variety of soil ecosystems ranging in pH (4.0 - 7.5). Prokaryotic and viral community structure were significantly influenced by soil pH at the local scale. Of 1,910 viral operational taxonomic units (vOTUs), 99% were restricted to pH 4.5 or 7.5 soil only. These were compared in gene sharing networks of populations from six other European and North American soil systems. A selection of viral clusters from acidic and neutral pH soils were more associated with those from the local gradient pH 4.5 or 7.5 soils, respectively. Results indicate that as with prokaryotes, soil pH is a factor structuring viral communities at the local and global scale.

ecology↗

bioRxiv2021

DNase treatment improves viral enrichment in agricultural soil viromes

The small genomes of most viruses make it difficult to fully capture viral diversity in metagenomes dominated by DNA from cellular organisms. Viral size-fraction metagenomics (viromics) protocols facilitate enrichment of viral DNA from environmental samples, and these protocols typically include a DNase treatment of the post-0.2 m viromic fraction to remove contaminating free DNA prior to virion lysis. However, DNase may also remove desirable viral genomic DNA (e.g., contained in virions compromised due to frozen storage or laboratory processing), suggesting that DNase-untreated viromes might be useful in some cases. In order to understand how virome preparation with and without DNase treatment influences the resultant data, here we compared 15 soil viromes (7 DNase-treated, 8 untreated) from 8 samples collected from agricultural fields prior to tomato planting. DNase-treated viromes yielded significantly more assembled viral contigs, contained significantly less non-viral microbial DNA, and recovered more viral populations (vOTUs) through read mapping. However, DNase-treated and untreated viromes were statistically indistinguishable, in terms of ecological patterns across viral communities. Although results suggest that DNase treatment is preferable where possible, in comparison to previously reported total metagenomes from the same samples, both DNase-treated and untreated viromes were significantly enriched in viral signatures by all metrics compared, including a ~225 times greater proportion of viral reads in untreated viromes compared to total metagenomes. Thus, even without DNase treatment, viromics was preferable to total metagenomics for capturing viral diversity in these soils, suggesting that preparation of DNase-untreated viromes can be worthwhile when DNase treatment is not possible. ImportanceViromics is becoming an increasingly popular method for characterizing soil viral communities. DNase treatment of the viral size fraction prior to DNA extraction is meant to reduce contaminating free DNA and is a common step within viromics protocols to ensure sequences are of viral origin. However, some samples may not be amendable to DNase treatment due to viral particles being compromised either in storage (i.e. frozen) or during other sample processing. To date, the effect of DNase treatment on the recovery of viruses and downstream ecological interpretations of soil viral communities is not thoroughly understood. This work sheds light on these questions and indicates that while DNase treatment of soil viromes improves recovery of viral populations, this improvement is modest in comparison to the gains made by viromics over total soil metagenomics. Further, DNase treatment may not be necessary to observe the ecological patterns structuring soil viral communities.

microbiology↗

bioRxiv2020

Minnesota peat viromes reveal terrestrial and aquatic niche partitioning for local and global viral populations

BackgroundPeatlands are expected to experience sustained yet fluctuating higher temperatures due to climate change, leading to increased microbial activity and greenhouse gas emissions. Despite mounting evidence for viral contributions to these processes in peatlands underlain with permafrost, little is known about viruses in other peatlands. More generally, soil viral biogeography and its potential drivers are poorly understood at both local and global scales. Here, 87 metagenomes and five viral size-fraction metagenomes (viromes) from a boreal peatland in northern Minnesota (the SPRUCE whole-ecosystem warming experiment and surrounding bog) were analyzed for dsDNA viral community ecological patterns, and the recovered viral populations (vOTUs) were compared to our curated PIGEON database of 266,805 vOTUs from diverse ecosystems. ResultsWithin the SPRUCE experiment, viral community composition was significantly correlated with peat depth, water content, and carbon chemistry, including CH4 and CO2 concentrations, but not with temperature during the first two years of warming treatments. Peat vOTUs with aquatic-like signatures (shared predicted protein content with marine and/or freshwater vOTUs) were significantly enriched in more waterlogged surface peat depths. Predicted host ranges for SPRUCE vOTUs were relatively narrow, generally within a single bacterial genus. Of the 4,326 SPRUCE vOTUs, 164 were previously detected in other soils, mostly peatlands. None of the previously identified 202,372 marine and freshwater vOTUs in our PIGEON database were detected in SPRUCE peat, but 1.9% of 78,203 genus-level viral clusters (VCs) were shared between soil and aquatic environments. On a per-sample basis, vOTU recovery was 32 times higher from viromes compared to total metagenomes. ConclusionsResults suggest strong viral "species" boundaries between terrestrial and aquatic ecosystems and to some extent between peat and other soils, with differences less pronounced at the "genus" level. The significant enrichment of aquatic-like vOTUs in more waterlogged peat suggests that viruses may also exhibit niche partitioning on more local scales. These patterns are presumably driven in part by host ecology, consistent with the predicted narrow host ranges. Although more samples and increased sequencing depth improved vOTU recovery from total metagenomes, the substantially higher per-sample vOTU recovery after viral particle enrichment highlights the utility of soil viromics.

microbiology↗

bioRxiv2019

Dormancy dynamics and dispersal contribute to soil microbiome resilience

In disturbance ecology, stability is composed of resistance to change and resilience towards recovery after the disturbance subsides. Two key microbial mechanisms that can support microbiome stability include dormancy and dispersal. Specifically, microbial populations that are sensitive to disturbance can be re-seeded by local dormant pools of viable and reactivated cells, or by immigrants dispersed from regional metacommunities. However, it is difficult to quantify the contributions of these mechanisms to stability without, first, distinguishing the active from inactive membership, and, second, distinguishing the populations recovered by local resuscitation from those recovered by dispersed immigrants. Here, we investigate the contributions of dormancy dynamics (activation and inactivation), and dispersal to soil microbial community resistance and resilience. We designed a replicated, 45-week time-series experiment to quantify the responses of the active soil microbial community to a thermal press disturbance, including control mesocosms, disturbed mesocosms without dispersal, and disturbed mesocosms with dispersal after the release of the stressor. Communities were sensitive within one week of warming. Though the disturbed mesocosms did not fully recover within 29 weeks, resuscitation of thermotolerant taxa was key for community transition during the press, and both resuscitation of opportunistic taxa and immigration contributed to community resilience. Also, mesocosms with dispersal were more resilient than mesocosms without. This work advances the mechanistic understanding of how microbiomes respond to disturbances in their environment.

ecology↗

bioRxiv2018

Assembly and seasonality of core phyllosphere microbiota on perennial biofuel crops

Perennial grasses are promising feedstocks for biofuel production. The phyllosphere (aerial surfaces) of these cellulosic crops provide a sizable surface area of microbial habitation. Leaf microbial communities may benefit the host plant, have consequence for biomass deconstruction, and interact with foliar pathogens. Here, we characterized the origins, diversity, and assembly of bacterial and archaeal communities of two perennial cellulosic feedstocks: switchgrass (Panicum virgatum L.) and miscanthus (Miscanthus x giganteus). We used 16S rRNA gene sequencing to assess microbiome structure on leaves and soils, following crop phenology every three weeks from pre-emergence through senescence for one miscanthus growing season and two consecutive switchgrass seasons. We found abundant and persistent core leaf taxa that originated in soil but were adapted for life on the leaf, rather than vagabonds that randomly disperse from air or soil. Seasonal and host-specific assembly suggested a functional relationship between the phyllosphere microbiomes and plants. This foundational knowledge advances goals to leverage native microbiomes to promote crop wellness and productivity in the field, and specifically in support of biofuels agriculture.

microbiology↗

bioRxiv2018

Ecological selection for small microbial genomes along a temperate-to-thermal soil gradient

Small bacterial and archaeal genomes provide insights into the minimal requirements for life1 and seem to be widespread on the microbial phylogenetic tree2. We know that evolutionary processes, mainly selection and drift, can result in microbial genome reduction 3,4. However, we do not know the precise environmental pressures that constrain genome size in free-living microorganisms. A study including isolates 5 has shown that bacteria with high optimum growth temperatures, including thermophiles, often have small genomes 6. It is unclear how well this relationship may extend generally to microorganisms in nature 7,8, and in particular to those microbes inhabiting complex and highly variable environments like soil 3,6,9. To understand the genomic traits of thermally-adapted microorganisms, here we investigated bacterial and archaeal metagenomes from a 45{degrees}C gradient of temperate-to-thermal soils overlying the ongoing Centralia, Pennsylvania (USA) coal seam fire. There was a strong relationship between average genome size and temperature: hot soils had small genomes relative to ambient soils (Pearsons r = -0.910, p < 0.001). There was also an inverse relationship between soil temperature and cell size (Pearsons r = -0.65, p = 0.021), providing evidence that cell and genome size in the wild are together constrained by temperature. Notably, hot soils had different community structures than ambient soils, implicating ecological selection for thermo-tolerant cells that had small genomes, rather than contemporary genome streamlining within the local populations. Hot soils notably lacked genes for described two-component regulatory systems and antimicrobial production and resistance. Our work provides field evidence for the inverse relationship between microbial genome size and temperature requirements in a diverse, free-living community over a wide range of temperatures that support microbial life. Our findings demonstrate that ecological selection for thermophiles and thermo-tolerant microorganisms can result in smaller average genome sizes in situ, possibly because they have small genomes reminiscent of a more ancestral state.

microbiology↗