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Pyrogenic organic matter (PyOM) additions to soils can have large impacts on soil organic carbon (SOC) cycling. As the soil microbial community drives SOC fluxes, understanding how PyOM additions affect soil microbes is essential to understanding how PyOM affects SOC. We studied SOC dynamics and surveyed soil bacterial communities after OM additions in a field experiment. We produced and mixed in either 350 °C corn stover PyOM or an equivalent initial amount of dried corn stover to a Typic Fragiudept soil. Stover increased SOC-derived and total CO 2 fluxes (up to 6x), and caused rapid and persistent changes in bacterial community composition over 82 days. In contrast, PyOM only temporarily increased total soil CO 2 fluxes (up to 2x) and caused fewer changes in bacterial community composition. Of the operational taxonomic units (OTUs) that increased in response to PyOM additions, 70% also responded to stover additions. These OTUs likely thrive on easily mineralizable carbon (C) that is found both in stover and, to a lesser extent, in PyOM. In contrast, we also identified unique PyOM responders, which may respond to substrates such as polyaromatic C. In particular, members of Gemmatimonadetes tended to increase in relative abundance in response to PyOM but not to fresh organic matter. We identify taxa to target for future investigations of the mechanistic underpinnings of ecological phenomena associated with PyOM additions to soil.

Our study reveals the ecogenomic traits of microorganisms participating in the cellulose economy of soil. We identified three major categories of participants in this economy: (i) independent primary degraders, (ii) interdependent primary degraders, and (iii) secondary consumers (mutualists, opportunists, and parasites). Microorganisms that degrade cellulose utilize extracellular reactions that yield free by-products which can promote interactions with noncellulolytic organisms. We hypothesized that these interactions determine the ecological and physiological traits governing the fate of cellulosic carbon (C) in soil. We performed comparative genomics with genome bins from a shotgun metagenomic-stable isotope probing experiment to characterize the attributes of cellulolytic and noncellulolytic taxa accessing 13 C from cellulose. We hypothesized that cellulolytic taxa would exhibit competitive traits that limit access, while noncellulolytic taxa would display greater metabolic dependency, such as signatures of adaptive gene loss. We tested our hypotheses by evaluating genomic traits indicative of competitive exclusion or metabolic dependency, such as antibiotic production, growth rate, surface attachment, biomass degrading potential, and auxotrophy. The most 13 C-enriched taxa were cellulolytic Cellvibrio ( Gammaproteobacteria ) and Chaetomium ( Ascomycota ), which exhibited a strategy of self-sufficiency (prototrophy), rapid growth, and competitive exclusion via antibiotic production. Auxotrophy was more prevalent in cellulolytic Actinobacteria than in cellulolytic Proteobacteria , demonstrating differences in dependency among cellulose degraders. Noncellulolytic taxa that accessed 13 C from cellulose ( Planctomycetales , Verrucomicrobia , and Vampirovibrionales ) were also more dependent, as indicated by patterns of auxotrophy and 13 C labeling (i.e., partial labeling or labeling at later stages). Major 13 C-labeled cellulolytic microbes (e.g., Sorangium, Actinomycetales, Rhizobiales , and Caulobacteraceae ) possessed adaptations for surface colonization (e.g., gliding motility, hyphae, attachment structures) signifying the importance of surface ecology in decomposing particulate organic matter. Our results demonstrated that access to cellulosic C was accompanied by ecological trade-offs characterized by differing degrees of metabolic dependency and competitive exclusion. IMPORTANCE Our study reveals the ecogenomic traits of microorganisms participating in the cellulose economy of soil. We identified three major categories of participants in this economy: (i) independent primary degraders, (ii) interdependent primary degraders, and (iii) secondary consumers (mutualists, opportunists, and parasites). Trade-offs between independent primary degraders, whose adaptations favor antagonism and competitive exclusion, and interdependent and secondary degraders, whose adaptations favor complex interspecies interactions, are expected to affect the fate of microbially processed carbon in soil. Our findings provide useful insights into the ecological relationships that govern one of the planet’s most abundant resources of organic carbon. Furthermore, we demonstrate a novel gradient-resolved approach for stable isotope probing, which provides a cultivation-independent, genome-centric perspective into soil microbial processes.

The khmer package is a freely available software library for working efficiently with fixed length DNA words, or k-mers. khmer provides implementations of a probabilistic k-mer counting data structure, a compressible De Bruijn graph representation, De Bruijn graph partitioning, and digital normalization. khmer is implemented in C++ and Python, and is freely available under the BSD license at  https://github.com/dib-lab/khmer/.

We have identified Streptomyces sister-taxa which share a recent common ancestor and nearly identical small subunit (SSU) rRNA gene sequences, but inhabit distinct geographic ranges demarcated by latitude and have sufficient genomic divergence to represent distinct species. Here, we explore the evolutionary dynamics of secondary metabolite biosynthetic gene clusters (SMGCs) following lineage divergence of these sister-taxa. These sister-taxa strains contained 310 distinct SMGCs belonging to 22 different gene cluster classes. While there was broad conservation of these 22 gene cluster classes among the genomes analyzed, each individual genome harbored a different number of gene clusters within each class. A total of nine SMGCs were conserved across nearly all strains, but the majority (57%) of SMGCs were strain-specific. We show that while each individual genome has a unique combination of SMGCs, this diversity displays lineage-level modularity. Overall, the northern-derived (NDR) clade had more SMGCs than the southern-derived (SDR) clade (40.7 ± 3.9 and 33.8 ± 3.9, mean and S.D., respectively). This difference in SMGC content corresponded with differences in the number of predicted open reading frames (ORFs) per genome (7775 ± 196 and 7093 ± 205, mean and S.D., respectively) such that the ratio of SMGC:ORF did not differ between sister-taxa genomes. We show that changes in SMGC diversity between the sister-taxa were driven primarily by gene acquisition and deletion events, and these changes were associated with an overall change in genome size which accompanied lineage divergence.

Viruses represent important test cases for data federation due to their genome size and the rapid increase in sequence data in publicly available databases. However, some consequences of previously decentralized (unfederated) data are lack of consensus or comparisons between feature annotations. Unifying or displaying alternative annotations should be a priority both for communities with robust entry representation and for nascent communities with burgeoning data sources. To this end, during this three-day continuation of the Virus Hunting Toolkit codeathon series (VHT-2), a new integrated and federated viral index was elaborated. This Federated Index of Viral Experiments (FIVE) integrates pre-existing and novel functional and taxonomy annotations and virus–host pairings. Variability in the context of viral genomic diversity is often overlooked in virus databases. As a proof-of-concept, FIVE was the first attempt to include viral genome variation for HIV, the most well-studied human pathogen, through viral genome diversity graphs. As per the publication of this manuscript, FIVE is the first implementation of a virus-specific federated index of such scope. FIVE is coded in BigQuery for optimal access of large quantities of data and is publicly accessible. Many projects of database or index federation fail to provide easier alternatives to access or query information. To this end, a Python API query system was developed to enhance the accessibility of FIVE.

Biological soil crusts (BSCs) are key components of ecosystem productivity in arid lands and they cover a substantial fraction of the terrestrial surface. In particular, BSC N 2 -fixation contributes significantly to the nitrogen (N) budget of arid land ecosystems. In mature crusts, N 2 -fixation is largely attributed to heterocystous cyanobacteria; however, early successional crusts possess few N 2 -fixing cyanobacteria and this suggests that microorganisms other than cyanobacteria mediate N 2 -fixation during the critical early stages of BSC development. DNA stable isotope probing with 15 N 2 revealed that Clostridiaceae and Proteobacteria are the most common microorganisms that assimilate 15 N 2 in early successional crusts. The Clostridiaceae identified are divergent from previously characterized isolates, though N 2 -fixation has previously been observed in this family. The Proteobacteria identified share >98.5% small subunit rRNA gene sequence identity with isolates from genera known to possess diazotrophs (for example, Pseudomonas , Klebsiella , Shigella and Ideonella ). The low abundance of these heterotrophic diazotrophs in BSCs may explain why they have not been characterized previously. Diazotrophs have a critical role in BSC formation and characterization of these organisms represents a crucial step towards understanding how anthropogenic change will affect the formation and ecological function of BSCs in arid ecosystems.

Pyrogenic organic matter (PyOM) additions to soils can have large impacts on soil organic carbon (SOC) cycling. As the soil microbial community drives SOC fluxes, understanding how PyOM additions affect soil microbes is essential to understanding how PyOM affects SOC. We studied SOC dynamics and surveyed soil bacterial communities after OM additions in a field experiment. We produced and mixed in either 350 °C corn stover PyOM or an equivalent initial amount of dried corn stover to a Typic Fragiudept soil. Stover increased SOC-derived and total CO2 fluxes (up to 6x), and caused rapid and persistent changes in bacterial community composition over 82 days. In contrast, PyOM only temporarily increased total soil CO2 fluxes (up to 2x) and caused fewer changes in bacterial community composition. Of the operational taxonomic units (OTUs) that increased in response to PyOM additions, 70% also responded to stover additions. These OTUs likely thrive on easily mineralizable carbon (C) that is found both in stover and, to a lesser extent, in PyOM. In contrast, we also identified unique PyOM responders, which may respond to substrates such as polyaromatic C. In particular, members of Gemmatimonadetes tended to increase in relative abundance in response to PyOM but not to fresh organic matter. As a result, we identify taxa to target for future investigations of the mechanistic underpinnings of ecological phenomena associated with PyOM additions to soil.

To better understand the diversity of mechanisms for stromatolite morphogenesis as well as the diversity of microorganisms and microbial metabolisms associated with stromatolites it is imperative to describe the biological attributes of the full diversity of \"living\" stromatolite-like geobiological structures worldwide. It is of additional interest to describe geographically and geochemically comparable ecosystems but lacking stromatolites to stromatolite-forming environments to unravel the geochemical and microbiological aspects of stromatolite morphogenesis. Here we present a living stromatolite system in a Yellowstone National Park (YNP) hot spring that exhibits features in contrast to many popularly studied modern stromatolite analogs. Most notably, the YNP stromatolites are more finely laminated than living marine stromatolites and may be a more suitable textural analog to finely laminated stromatolites found in the rock record. The YNP stromatolites are composed of silica-encrusted cyanobacterial mats. The predominant lithofacies of the YNP stromatolite is comprised of silica-encrusted filaments and is distinctly laminated. The laminated quality of the main lithofacies is due to an alternating—possibly on a diurnal cycle—growth orientation of filamentous cyanobacteria. Two cyanobacterial mat types grow on the stromatolite surfaces and are preserved as two distinct lithofacies. One mat is present when the stromatolites are submerged or at the water-atmosphere interface and the other when stromatolites protrude from the hot spring. The lithofacies created by the encrustation of submerged mats constitutes the bulk of the stromatolites, is comprised of silica-encrusted filaments, and is distinctly laminated. To better understand the cyanobacterial membership and community structure differences between the mats, we collected mat samples from each type. Molecular methods revealed that submerged mat cyanobacteria were predominantly one novel phylotype while the exposed mats were predominantly heterocystous phylotypes (Chlorogloeopsis HTF and Fischerella). The cyanobacterium dominating the submerged mat type does not belong in any of the subphylum groups of cyanobacteria recognized by the Ribosomal Database Project and has also been found in association with travertine stromatolites in a Southwest Japan hot spring. Cyanobacterial membership profiles indicate that the heterocystous phylotypes are 'rare biosphere' members of the submerged mats. The heterocystous phylotypes likely emerge when the water level of the hot spring drops. Environmental pressures tied to water level such as sulfide exposure and possibly oxygen tension may inhibit the heterocystous types in submerged mats. In contrast to living marine examples where the interplay of pCO2 and [[special characters omitted]] is the main influence on microbial lithification, the lithification in the YNP system is driven by a rapid decrease in silica solubility between high-temperature subsurface water emitted from the hot spring vent and lower-temperature surface water. The continuously favorable conditions for rapid lithification in the hot spring system coupled to a cyanobacterial diurnal growth cycle that manifests itself as fine laminations in the stromatolite lithofacies leads to a growth rate for the YNP stromatolite on the order of centimeters of deposition in several months. The YNP system displays a perhaps overlooked mechanism for stromatolite morphogenesis and is compelling both for the presence of a seemingly unstudied cyanobacterium as well as a finely-laminated modern stromatolite analog of which there are few other examples.

Farmers grow sweetpotatoes worldwide and some sub-Saharan African and Asian diets include sweetpotato as a staple, yet the sweetpotato microbiome is conspicuously less studied relative to crops such as maize, soybean, and wheat. Studying sweetpotato microbiome ecology may reveal paths to engineer the microbiome to improve sweetpotato yield, and/or combat sweetpotato pests and diseases. We sampled sweetpotatoes and surrounding soil from two North Carolina farms. We took samples from sweetpotato fields under two different land management regimes, conventional and organic, and collected two sweetpotato cultivars, \"Beauregard\" and \"Covington\". By comparing SSU rRNA gene amplicon sequence profiles from sweetpotato storage root skin, rhizosphere, and surrounding soil we found the skin microbiome possessed the least composition heterogeneity among samples and lowest alpha-diversity, and, was significantly nested by the rhizosphere in amplicon sequence variant (ASV) membership. Many ASVs were specific to a single field and/or only found in either the skin, rhizosphere, or surrounding soil. Notably, sweetpotato skin enriched for Planctomycetaceae in relative abundance at both farms. This study elucidates underpinnings of sweetpotato microbiome community assembly, quantifies microbiome composition variance within a single farm, and reveals microorganisms associated with sweetpotato skin that belong to common but uncultured soil phylotypes.

The influence of resource availability on planktonic and biofilm microbial community membership is poorly understood. Heterotrophic bacteria derive some to all of their organic carbon (C) from photoautotrophs while simultaneously competing with photoautotrophs for inorganic nutrients such as phosphorus (P) or nitrogen (N). Therefore, C inputs have the potential to shift the competitive balance of aquatic microbial communities by increasing the resource space available to heterotrophs (more C) while decreasing the resource space available to photoautotrophs (less mineral nutrients due to increased competition from heterotrophs). To test how resource dynamics affect membership of planktonic communities and assembly of biofilm communities we amended a series of flow-through mesocosms with C to alter the availability of C among treatments. Each mesocosm was fed with unfiltered seawater and incubated with sterilized microscope slides as surfaces for biofilm formation. The highest C treatment had the highest planktonic heterotroph abundance, lowest planktonic photoautotroph abundance, and highest biofilm biomass. We surveyed bacterial 16S rRNA genes and plastid 23S rRNA genes to characterize biofilm and planktonic community membership and structure. Regardless of resource additions, biofilm communities had higher alpha diversity than planktonic communities in all mesocosms. Heterotrophic plankton communities were distinct from heterotrophic biofilm communities in all but the highest C treatment where heterotrophic plankton and biofilm communities resembled each other after 17 days. Unlike the heterotrophs, photoautotrophic plankton communities were different than photoautotrophic biofilm communities in composition in all treatments including the highest C treatment. Our results suggest that although resource amendments affect community membership and structure, microbial lifestyle (biofilm versus planktonic) has a stronger influence on community composition.