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Purpose [18F]-labeled positron emission tomography (PET) radioligands permit in vivo assessment of Alzheimer’s disease biomarkers, including aggregated neurofibrillary tau (NFT) with [18F]flortaucipir. Due to structural similarities of flortaucipir with some monoamine oxidase A (MAO-A) inhibitors, this study aimed to evaluate flortaucipir binding to MAO-A and MAO-B and any potential impact on PET interpretation. Methods [18F]Flortaucipir autoradiography was performed on frozen human brain tissue slices, and PET imaging was conducted in rats. Dissociation constants were determined by saturation binding, association and dissociation rates were measured by kinetic binding experiments, and IC50 values were determined by competition binding. Results Under stringent wash conditions, specific [18F]flortaucipir binding was observed on tau NFT-rich Alzheimer’s disease tissue and not control tissue. In vivo PET experiments in rats revealed no evidence of [18F]flortaucipir binding to MAO-A; pre-treatment with MAO inhibitor pargyline did not impact uptake or wash-out of [18F]flortaucipir. [18F]Flortaucipir bound with low nanomolar affinity to human MAO-A in a microsomal preparation in vitro but with a fast dissociation rate relative to MAO-A ligand fluoroethyl-harmol, consistent with no observed in vivo binding in rats of [18F]flortaucipir to MAO-A. Direct binding of flortaucipir to human MAO-B was not detected in a microsomal preparation. A high concentration of flortaucipir (IC50 of 1.3 μM) was found to block binding of the MAO-B ligand safinamide to MAO-B on microsomes suggesting that, at micromolar concentrations, flortaucipir weakly binds to MAO-B in vitro. Conclusion These data suggest neither MAO-A nor MAO-B binding will contribute significantly to the PET signal in cortical target areas relevant to the interpretation of [18F]flortaucipir.

The effects of sea level rise and coastal saltwater intrusion on wetland plants can extend well above the high-tide line due to drought, hurricanes, and groundwater intrusion. Research has examined how coastal salt marsh plant communities respond to increased flooding and salinity, but more inland coastal systems have received less attention. The aim of this study was to identify whether ground layer plants exhibit threshold responses to salinity exposure. We used two vegetation surveys throughout the Albemarle-Pamlico Peninsula (APP) of North Carolina, USA to assess vegetation in a low elevation landscape (≤ 3.8 m) experiencing high rates of sea level rise (3–4 mm/year). We examined the primary drivers of community composition change using Non-metric Multidimensional Scaling (NMDS) and used Threshold Indicator Taxa Analysis (TITAN) to detect thresholds of compositional change based on indicator taxa, in response to potential indicators of exposure to saltwater (Na, and the Σ Ca + Mg) and elevation. Salinity and elevation explained 64% of the variation in community composition, and we found two salinity thresholds for both soil Na+ (265 and 3843 g Na+/g) and Ca+ + Mg+ (42 and 126 µeq/g) where major changes in community composition occur on the APP. Similar sets of species showed sensitivity to these different metrics of salt exposure. Overall, our results showed that ground layer plants can be used as reliable indicators of salinity thresholds in coastal wetlands. These results can be used for monitoring salt exposure of ecosystems and for identifying areas at risk for undergoing future community shifts.

Salinization of freshwater ecosystems impacts carbon cycling, a particular concern for coastal wetlands, which are important agents of carbon sequestration. Previous experimental work using salt additions as a proxy for sea level rise, reveals widely divergent effects of salt on soil carbon processes. We performed a laboratory salt addition experiment on two different types of wetland soils (Ponzer muck and Hyde loam, both poorly drained organic soils) from the Coastal Plain of North Carolina. We used a commercial aquarium salt mix to make treatment solutions of 0, 2.5 and 10 ppt salinity and independently manipulated solution pH (5.5, 7.2, 8.8) for a full factorial experimental design. Our goal was to identify the effects of increasing ionic strength and increasing soil solution pH on soil carbon solubility and turnover. Microbial respiration and dissolved organic carbon solubility were depressed by marine salts, while pH manipulation alone had minimal effect. The addition of marine salts substantially reduced rates of carbon mineralization, reduced carbon solubility, and preferentially reduced the abundance of phenolic and aromatic organic molecules in solution. In the more acidic Ponzer muck, where salt additions dropped the pH from > 5 to

Background and Aims Bacterial swarming, a collective movement on a surface, has rarely been associated with human pathophysiology. This study aims to define a role for bacterial swarmers in amelioration of intestinal stress. Methods We developed a polymicrobial plate agar assay to detect swarming and screened mice and humans with intestinal stress and inflammation. From chemically induced colitis in mice, as well as humans with inflammatory bowel disease, we developed techniques to isolate the dominant swarmers. We developed swarm-deficient but growth and swim-competent mutant bacteria as isogenic controls. We performed bacterial reinoculation studies in mice with colitis, fecal 16S, and meta-transcriptomic analyses, as well as in vitro microbial interaction studies. Results We show that bacterial swarmers are highly predictive of intestinal stress in mice and humans. We isolated a novel Enterobacter swarming strain, SM3, from mouse feces. SM3 and other known commensal swarmers, in contrast to their mutant strains, abrogated intestinal inflammation in mice. Treatment of colitic mice with SM3, but not its mutants, enriched beneficial fecal anaerobes belonging to the family of Bacteroidales S24-7. We observed SM3 swarming associated pathways in the in vivo fecal meta-transcriptomes. In vitro growth of S24-7 was enriched in presence of SM3 or its mutants; however, because SM3, but not mutants, induced S24-7 in vivo, we concluded that swarming plays an essential role in disseminating SM3 in vivo. Conclusions Overall, our work identified a new but counterintuitive paradigm in which intestinal stress allows for the emergence of swarming bacteria; however, these bacteria act to heal intestinal inflammation.

Changes in fire frequency from historical norms are becoming more frequent due to both changes in management and climate change factors. There is uncertainty about whether increasing fire frequency will lead to decreased carbon pools due to shorter inter-fire recovery periods, or increased carbon pools due to lowered fire intensity due to lighter fuel loads. Additionally, data are needed to determine whether plant and soil carbon pools respond similarly and whether ecosystem responses are consistent across environmental gradients that can affect fire intensity, such as soil moisture. We measured soil and vegetation carbon pools and fluxes at sites that had experienced different experimental burn treatments over the previous 8 years and across a range of soil moisture in a longleaf pine (Pinus palustris) ecosystem in North Carolina, USA. We found that increasing fire frequency, assessed by either the number of days since a previous fire or the number of fires a plot had experienced over the previous 8 years, significantly reduced carbon stocks in the litter pool and soil carbon pool and reduced the productivity of understory plants. Total carbon stocks also significantly declined, and there was a marginally significant shift away from soil carbon and toward tree carbon as being the dominant carbon pool in the system with increasing fire. None of the results showed any interaction with soil moisture, suggesting that in this landscape, fire effects are consistent across an important environmental gradient. Over the timeframe of this study, management that increases prescribed fire frequency appears to reduce carbon storage.

BACKGROUND Infants are at a high risk of acquiring fatal infections, and their treatment relies on functioning antibiotics. Antibiotic resistance genes (ARGs) are present in high numbers in antibiotic-naive infants' gut microbiomes, and infant mortality caused by resistant infections is high. The role of antibiotics in shaping the infant resistome has been studied, but there is limited knowledge on other factors which affect the antibiotic resistance burden of the infant gut. OBJECTIVES Our objectives were to determine the impact of early exposure to formula on the ARG load in neonates and infants born either pre- or full-term. Our hypotheses were that diet causes a selective pressure that influences the microbial community of the infant gut, and formula exposure would increase the abundance of taxa that carry ARGs. DESIGN Cross-sectionally sampled gut metagenomes of 46 neonates were used to build a generalized linear model to determine the impact of diet on ARG loads in neonates. The model was cross-validated using neonate metagenomes gathered from public databases using our custom statistical pipeline for cross-validation. RESULTS Formula-fed neonates had higher relative abundances of opportunistic pathogens such as Staphylococcus aureus, Staphylococcus epidermidis, Klebsiella pneumoniae, Klebsiella oxytoca, and Clostridioides difficile. The relative abundance of ARGs carried by gut bacteria was 69% higher in the formula receiving group (fold change 1.69, (95% CI 1.12, 2.55), P = 0.013, n = 180) compared to exclusively human milk-fed infants. The formula-fed infants also had significantly less typical infant bacteria such as bifidobacteria that have potential health benefits. CONCLUSIONS The novel finding that formula exposure is correlated with a higher neonatal ARG burden lays the foundation that clinicians should consider feeding mode in addition to antibiotic use during the first months of life to minimize the proliferation of antibiotic-resistant gut bacteria in infants.Clinical trial registry number: The Institutional Review Board of Pennsylvania State University https://irb.upenn.edu/, USA (IRB #35925) approved the study.

[[Under stringent wash conditions, specific [These data suggest neither MAO-A nor MAO-B binding will contribute significantly to the PET signal in cortical target areas relevant to the interpretation of [

There is an increasing need to better understand how and why invasion impacts differ across heterogeneous landscapes. One hypothesis predicts invader impacts are greatest where the invader is most abundant (the mass ratio hypothesis; MRH). Alternatively, invader impacts may be greatest in communities where the nutrient acquisition strategies of the invader are most dissimilar from those of native species (the nutrient economy dissimilarity hypothesis; NEDH). We tested whether the effects of an invasive grass, Microstegium vimineum, on soil biogeochemistry were best explained by MRH, NEDH, or both. At three locations (Indiana, North Carolina, and Georgia), invaded and reference plots were established across a nutrient economy gradient. Plots varied in the relative abundance of arbuscular mycorrhizal (AM) vs. ectomycorrhizal (ECM) associated overstory trees, reflecting gradients in biotic nutrient acquisition strategies and edaphic factors. At two locations, we found NEDH predicted invader effects on soil conditions. The net effect of M. vimineum homogenized soil properties across the nutrient economy gradient towards conditions consistent with AM-dominated stands; as such, the nutrient economy gradients observed in uninvaded plots were mostly absent in invaded plots. At one location with high N availability and intermediate acidity, both ECM-dominance (NEDH) and invader abundance (MRH) predicted differences in soil moisture, pH, and nitrification rates. Collectively, these results suggest the biogeochemical consequences of M. vimineum depend, in part, on pre-invasion soil nutrient economies. Where pre-invasion conditions are known, we provide a scalable and predictive approach to determine where impacts on biogeochemical cycling of C and N may be greatest.

Nonalcoholic fatty liver disease is the leading cause of liver disease worldwide and can progress to nonalcoholic steatohepatitis (NASH) through physical inactivity and gut dysbiosis.1 Exercise training reverses gut dysbiosis in non-NASH persons with obesity and in NASH animal models.2,3 Consequently, we conducted a proof-of-concept study investigating the effect of exercise training on gut dysbiosis in NASH patients.

Exercise influences metabolic parameters in part by modulating redox stress and as recently suggested, by affecting the gut microbiome. However, whether excess endogenous antioxidant potentiates or interferes with the beneficial effects of exercise on the gut microbiome is not known. A comparison of the gut microbiome of C57Bl6 (C57/WT) mice to the 'stress-less' catalase overexpressing mice models ([Tg(CAT)± ] and Bob-Cat), that were either exercised or remained sedentary, showed differences in both alpha and beta diversity. The significant variation was explained by genotypes along with exercise, suggesting a synergistic relationship between exercise and genotypic traits. Linear discriminant analysis effect size (LEfSe) analysis also revealed differential taxa within the exercised/genotype cohorts in contrast to those within sedentary/genotype cohorts. Functional pathway predictions from PICRUSt2 showed enrichment for the metabolism of short-chain fatty acids, butanoate and propanoate pathways in exercised groups. Spearman correlations between enriched taxa and metabolic parameters showed correlations with body or fat weight in some of the cohorts. However, there were significant correlations of differential taxa among all cohorts against parameters that predict energy metabolism, such as respiratory exchange ratio and energy expenditure. Overall, our study showed that there was a synergistic beneficial influence of antioxidant overexpression and exercise on the gut microbiome.

Rationale: There is incomplete knowledge of the impact of bone marrow cells on the gut microbiome and gut barrier function. Objective: We postulated that diabetes mellitus and systemic ACE2 (angiotensin-converting enzyme 2) deficiency would synergize to adversely impact both the microbiome and gut barrier function. Methods and Results: Bacterial 16S rRNA sequencing and metatranscriptomic analysis were performed on fecal samples from wild-type, ACE2 −/y , Akita (type 1 diabetes mellitus), and ACE2 −/y -Akita mice. Gut barrier integrity was assessed by immunofluorescence, and bone marrow cell extravasation into the small intestine was evaluated by flow cytometry. In the ACE2 −/y -Akita or Akita mice, the disrupted barrier was associated with reduced levels of myeloid angiogenic cells, but no increase in inflammatory monocytes was observed within the gut parenchyma. Genomic and metatranscriptomic analysis of the microbiome of ACE2 −/y -Akita mice demonstrated a marked increase in peptidoglycan-producing bacteria. When compared with control cohorts treated with saline, intraperitoneal administration of myeloid angiogenic cells significantly decreased the microbiome gene expression associated with peptidoglycan biosynthesis and restored epithelial and endothelial gut barrier integrity. Also indicative of diabetic gut barrier dysfunction, increased levels of peptidoglycan and FABP-2 (intestinal fatty acid-binding protein 2) were observed in plasma of human subjects with type 1 diabetes mellitus (n=21) and type 2 diabetes mellitus (n=23) compared with nondiabetic controls (n=23). Using human retinal endothelial cells, we determined that peptidoglycan activates a noncanonical TLR-2 (Toll-like receptor 2) associated MyD88 (myeloid differentiation primary response protein 88)-ARNO (ADP-ribosylation factor nucleotide-binding site opener)-ARF6 (ADP-ribosylation factor 6) signaling cascade, resulting in destabilization of p120-catenin and internalization of VE-cadherin as a mechanism of deleterious impact of peptidoglycan on the endothelium. Conclusions: We demonstrate for the first time that the defect in gut barrier function and dysbiosis in ACE2 −/y -Akita mice can be favorably impacted by exogenous administration of myeloid angiogenic cells.

Increases in carbon (C) inputs can augment soil organic matter (SOM), or reduce SOM by accelerating decomposition. Thus, there is a need to understand how and why ecosystems differ in their sensitivity to C inputs. Invasive plants that invade wide-ranging habitats, accumulate biomass rapidly, and contribute copious amounts of C to soil can be ideal for addressing this gap. We quantified the effects of the invasive C4 grass, Microstegium vimineum, on SOM in three temperate forests across plots varying in their relative abundance of arbuscular mycorrhizal (AM) versus ectomycorrhizal (ECM) trees. We hypothesized that invasion would differentially affect SOM along the mycorrhizal gradient owing to recognized patterns in nitrogen availability (AM > ECM) and the proportion of unprotected SOM (ECM > AM). Across all sites, M. vimineum was associated with lower particulate organic matter (POM) in ECM-dominated plots, consistent with our hypothesis that invader-derived C inputs should stimulate decomposers to acquire nitrogen from unprotected SOM in soils with low nitrogen availability. However, the pattern of lower POM in the ECM-dominated soils was offset by greater mineral-associated organic matter (MAOM)—and isotopic data suggest this was largely driven by native- rather than invader-derived SOM—implying an invasion-associated transfer of native-derived POM into MAOM. Our results demonstrate a context-dependent shift in the form of SOM in a system with presumably enhanced C inputs. This finding suggests a need to look beyond changes in total SOM stocks, as intrinsic SOM changes could lead to important long-term feedbacks on invasion or priming effects.

The interactions between a host and its resident microbes form complicated networks that can affect host physiology. Disentangling these host-microbe interactions can help us better understand mechanisms by which bacteria affect hosts, while also defining the integral commensal protection that host-associated microbiota offer to promote health. Here we utilize a tractable genetic model organism, Caenorhabditis elegans, to study the effects of host environments on bacterial gene expression and metabolic pathways. First, we compared the transcriptomic profiles of E. coli OP50 in vitro (on agar plates) versus in vivo (fed to C. elegans host). Our data revealed that 110 biosynthetic genes were enriched in host-associated E. coli. Several of these expressed genes code for the precursors and products needed for the synthesis of lipopolysaccharides (LPS), which are important for innate immune and stress responses, as well as pathogenicity. Secondly, we compared the transcriptomic profiles of E. coli fed to hosts with different genetic backgrounds, including the long-lived daf-2/insulin like growth factor (IGF) receptor and short lived daf-16/FOXO transcription factor mutants. We find that hosts genetics also alters bacterial metabolic pathways. Given that bacteria influence host health, this transcriptomics approach can elucidate genes mediating host aging.

QUESTIONS: Disturbances can cause fluctuations in resource availability that influence plant performance. In systems with such dynamics, inter‐specific differences in resource capture may promote co‐existence by partitioning competition between periods of high or low resource availability. Such differences in resource use strategy have been described with the Plant Economics Spectrum, which hypothesizes that functions related to resource use and processing should co‐vary and can be predicted from plant traits. In pyrogenic systems, fires are associated with short‐term increases in soil nitrogen availability (“pulses”), and thus contribute to a fluctuating resource supply. In this study, we sought to understand whether plants differed in their capacity to capture a nitrogen pulse, and to what extent that ability influenced biomass recovery. METHODS: In two consecutive greenhouse experiments, we tested whether two functions — nitrogen assimilation (Experiment 1) and biomass regrowth after disturbance (Experiment 2) — co‐varied, and how each function corresponded to leaf and root functional traits. RESULTS: In Experiment 1, four co‐occurring shrubs differed in their temporal patterns of nitrogen uptake, and nitrogen uptake was positively correlated with resource‐acquisitive leaf traits (leaf percent nitrogen). In Experiment 2, the biomass regrowth of a resource acquisitive and a resource conservative species was the same regardless of competitive environment (i.e., when grown in pots of mixed‐species or same‐species pairs). Rather than being associated with the capture of new nitrogen, biomass resprouting of both species was associated with the size of below‐ground resource stores and specific root length. CONCLUSIONS: Our work suggests that resource acquisition and processing may be decoupled from each other after disturbance, and also highlights the need for explicit tests of the relationships between root traits and above‐ground plant function.

Climate change is driving ecological shifts in coastal regions of the world, where low topographic relief makes ecosystems particularly vulnerable to sea-level rise, salinization, storm surge, and other effects of global climate change. The consequences of rising water tables and salinity can penetrate well inland, and lead to particularly dramatic changes in freshwater forested wetlands dominated by tree species with low salt tolerance. The resulting loss of coastal forests could have significant implications to the coastal carbon cycle. We quantified the rates of vegetation change including land loss, forest loss, and shrubland expansion in North Carolina's largest coastal wildlife refuge over 35 yr. Despite its protected status, and in the absence of any active forest management, 32% (31,600 hectares) of the refuge area has changed landcover classification during the study period. A total of 1,151 hectares of land was lost to the sea and ~19,300 hectares of coastal forest habitat was converted to shrubland or marsh habitat. As much as 11% of all forested cover in the refuge transitioned to a unique land cover type-"ghost forest"-characterized by standing dead trees and fallen tree trunks. The formation of this ghost forest transition state peaked prominently between 2011 and 2012, following Hurricane Irene and a 5-yr drought, with 4,500 ± 990 hectares of ghost forest forming during that year alone. This is the first attempt to map and quantify coastal ghost forests using remote sensing. Forest losses were greatest in the eastern portion of the refuge closest to the Croatan and Pamlico Sounds, but also occurred much further inland in low-elevation areas and alongside major canals. These unprecedented rates of deforestation and land cover change due to climate change may become the status quo for coastal regions worldwide, with implications for wetland function, wildlife habitat, and global carbon cycling.

The gut is a well-established route of infection and target for viral damage by SARS-CoV-2. This is supported by the clinical observation that about half of COVID-19 patients exhibit gastrointestinal (GI) symptoms. We asked whether the analysis of plasma could provide insight into gut barrier dysfunction in patients with COVID-19 infection. Plasma samples of COVID-19 patients (n=30) and healthy control (n=16) were collected during hospitalization. Plasma microbiome was analyzed using 16S rRNA sequencing, metatranscriptomic analysis, and gut permeability markers including FABP-2, PGN and LPS in both patient cohorts. Almost 65% (9 out 14) COVID-19 patients showed abnormal presence of gut microbes in their bloodstream. Plasma samples contained predominately Proteobacteria, Firmicutes, and Actinobacteria. The abundance of gram-negative bacteria (Acinetobacter, Nitrospirillum, Cupriavidus, Pseudomonas, Aquabacterium, Burkholderia, Caballeronia, Parabhurkholderia, Bravibacterium, and Sphingomonas) was higher than the gram-positive bacteria (Staphylococcus and Lactobacillus) in COVID-19 subjects. The levels of plasma gut permeability markers FABP2 (1282±199.6 vs 838.1±91.33; p=0.0757), PGN (34.64±3.178 vs 17.53±2.12; pvs 249.6±17.06; p=0.0049) were higher in COVID-19 patients compared to healthy subjects. These findings support that the intestine may represent a source for bacteremia and may contribute to worsening COVID-19 outcomes. Therapies targeting the gut and prevention of gut barrier defects may represent a strategy to improve outcomes in COVID-19 patients.

Characterization of the gut microbiome may aid understanding and management of natural and experimental disease states in research animals, thereby promoting reproducibility. In this study, the rectal bacterial communities of three separate common marmoset (Callithrix jacchus) breeding colonies were defined using 16S rRNA sequencing of rectal swab samples. Study animals originated from two German colonies and a United States colony (JHU). The two German cohorts, previously fed the same diet, were imported into the JHU facility; they were then isolated, transitioned onto JHU diet, and then moved into rooms housing JHU animals. To dissect the contributions of diet and integration in shaping the rectal bacterial community, samples were collected from German origin marmosets upon JHU arrival (baseline), following diet transition (100 d), and following cohousing (390 d). Baseline and 390 d samples were collected from stably maintained JHU marmosets. Bacterial community composition was distinct between all three cohorts at baseline, suggesting that factors other than primary diet confer significant differences between captive populations. Beta-diversity of the animals from the two German colonies converged by 100 d but remained distinct from JHU sample beta-diversity throughout the 390-d study, indicating that diet had greater influence on bacterial community composition than did housing animals within the same room. Our results demonstrate substantial differences in gut bacteria between different captive marmoset colonies, with persistence of these differences following husbandry standardization and housing integration. Goals of rigor and reproducibility in research underscore the need to consider microbial differences between marmosets of diverse origin.ImportanceCharacterizing gut microbial populations is expected to promote health and enhance research reproducibility in animal studies. As use of common marmosets as animal models of human diseases expands, evaluating the marmoset gut bacterial community will be critical for interpreting research findings, especially as marmosets are prone to gastrointestinal inflammation. In this study, using 16S rRNA sequencing of rectal swab samples, we compared bacterial community among three captive colonies of marmosets at baseline and following importation of cohorts from two of the colonies into the third colony. Diet history had sustained influence on bacterial community composition, while housing the animals within the same room over a period of eight months did not appear to be a major factor. These persistent differences in marmoset gut bacterial community highlight the need for careful consideration of animal origin as a variable in marmoset research studies.

[Motivation]: Trait data are fundamental to the quantitative description of plant form and function. Although root traits capture key dimensions related to plant responses to changing environmental conditions and effects on ecosystem processes, they have rarely been included in large-scale comparative studies and global models. For instance, root traits remain absent from nearly all studies that define the global spectrum of plant form and function. Thus, to overcome conceptual and methodological roadblocks preventing a widespread integration of root trait data into large-scale analyses we created the Global Root Trait (GRooT) Database. GRooT provides ready to use data by combining the expertise of root ecologists with data mobilization and curation. Specifically, we (a) determined a set of core root traits relevant to the description of plant form and function based on an assessment by experts, (b) maximized species coverage through data standardization within and among traits, and (c) implemented data quality checks., [Main types of variables contained]: GRooT contains 114,222 trait records on 38 continuous root traits.Spatial location and grain: Global coverage with data from arid, continental, polar, temperate and tropical biomes. Data on root traits were derived from experimental studies and field studies., [Time period and grain]: Data were recorded between 1911 and 2019., [Major taxa and level of measurement]: GRooT includes root trait data for which taxonomic information is available. Trait records vary in their taxonomic resolution, with subspecies or varieties being the highest and genera the lowest taxonomic resolution available. It contains information for 184 subspecies or varieties, 6,214 species, 1,967 genera and 254 families. Owing to variation in data sources, trait records in the database include both individual observations and mean values., [Software format]: GRooT includes two csv files. A GitHub repository contains the csv files and a script in R to query the database., The study has been supported by the TRY initiative on plant traits (http://www.try-db.org). The TRY initiative and database are hosted, developed and maintained at the Max Planck Institute for Biogeochemistry, Jena, Germany. TRY is currently supported by DIVERSITAS/Future Earth and the German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig. Open access funding enabled and organized by Projekt DEAL.

Background and Aims Understanding impacts of altered disturbance regimes on community structure and function is a key goal for community ecology. Functional traits link species composition to ecosystem functioning. Changes in the distribution of functional traits at community scales in response to disturbance can be driven not only by shifts in species composition, but also by shifts in intraspecific trait values. Understanding the relative importance of these two processes has important implications for predicting community responses to altered disturbance regimes. Methods We experimentally manipulated fire return intervals in replicated blocks of a fire-adapted, longleaf pine (Pinus palustris) ecosystem in North Carolina, USA and measured specific leaf area (SLA), leaf dry matter content (LDMC) and compositional responses along a lowland to upland gradient over a 4 year period. Plots were burned between zero and four times. Using a trait-based approach, we simulate hypothetical scenarios which allow species presence, abundance or trait values to vary over time and compare these with observed traits to understand the relative contributions of each of these three processes to observed trait patterns at the study site. We addressed the following questions. (1) How do changes in the fire regime affect community composition, structure and community-level trait responses? (2) Are these effects consistent across a gradient of fire intensity? (3) What are the relative contributions of species turnover, changes in abundance and changes in intraspecific trait values to observed changes in community-weighted mean (CWM) traits in response to altered fire regime? Key Results We found strong evidence that altered fire return interval impacted understorey plant communities. The number of fires a plot experienced significantly affected the magnitude of its compositional change and shifted the ecotone boundary separating shrub-dominated lowland areas from grass-dominated upland areas, with suppression sites (0 burns) experiencing an upland shift and annual burn sites a lowland shift. We found significant effects of burn regimes on the CWM of SLA, and that observed shifts in both SLA and LDMC were driven primarily by intraspecific changes in trait values. Conclusions In a fire-adapted ecosystem, increased fire frequency altered community composition and structure of the ecosystem through changes in the position of the shrub line. We also found that plant traits responded directionally to increased fire frequency, with SLA decreasing in response to fire frequency across the environmental gradient. For both SLA and LDMC, nearly all of the observed changes in CWM traits were driven by intraspecific variation.

Whole microbial communities regularly merge with one another, often in tandem with their environments, in a process called community coalescence. Such events impose substantial changes: abiotic perturbation from environmental blending and biotic perturbation of community merging. We used an aquatic mixing experiment to unravel the effects of these perturbations on the whole microbiome response and on the success of individual taxa when distinct freshwater and marine communities coalesce. We found that an equal mix of freshwater and marine habitats and blended microbiomes resulted in strong convergence of the community structure toward that of the marine microbiome. The enzymatic potential of these blended microbiomes in mixed media also converged toward that of the marine, with strong correlations between the multivariate response patterns of the enzymes and of community structure. Exposing each endmember inocula to an axenic equal mix of their freshwater and marine source waters led to a 96% loss of taxa from our freshwater microbiomes and a 66% loss from our marine microbiomes. When both inocula were added together to this mixed environment, interactions amongst the communities led to a further loss of 29% and 49% of freshwater and marine taxa, respectively. Under both the axenic and competitive scenarios, the diversity lost was somewhat counterbalanced by increased abundance of microbial taxa that were too rare to detect in the initial inocula. Our study emphasizes the importance of the rare biosphere as a critical component of microbial community responses to community coalescence.

Bacterial swarming, a collective movement on a surface, in contrast to sessile biofilms, has rarely been associated with human pathophysiology in health and disease. Here, we report for the first time that bacterial swarmers are associated with protection against intestinal inflammation in a murine model of acute colitis. We show, the presence of bacterial swarmers is highly predictive of intestinal stress in mice, pigs, and humans. We isolated a novel Enterobacter swarming strain, SM3 from mouse feces. In mice, SM3 and other known commensal swarmers, in contrast to their respective swarming-deficient but swimming-competent isogenic strains, demonstrated significant protection from intestinal inflammation. Treatment with SM3 in colitic mice also paralleled a significant reduction in luminal oxygen concentration and enrichment of beneficial anaerobes. Overall, our work identifies a new paradigm in which intestinal stress, allows for the emergence of swarming bacteria, which in turn can protect and heal from intestinal inflammation.

[Aim] Intraspecific trait variation (ITV) within natural plant communities can be large, influencing local ecological processes and dynamics. Here, we shed light on how ITV in vegetative and floral traits responds to large‐scale abiotic and biotic gradients (i.e., climate and species richness). Specifically, we tested whether associations of ITV with temperature, precipitation and species richness were consistent with any of four hypotheses relating to stress tolerance and competition. Furthermore, we estimated the degree of correlation between ITV in vegetative and floral traits and how they vary along the gradients., [Location] Global., [Time period] 1975–2016., [Major taxa studied] Herbaceous and woody plants., [Methods] We compiled a dataset of 18,401 measurements of the absolute extent of ITV (measured as the coefficient of variation) in nine vegetative and seven floral traits from 2,822 herbaceous and woody species at 2,372 locations., [Results] Large‐scale associations between ITV and climate were trait specific and more prominent for vegetative traits, especially leaf morphology, than for floral traits. The ITV showed pronounced associations with climate, with lower ITV values in colder areas and higher values in drier areas. The associations of ITV with species richness were inconsistent across traits. Species‐specific associations across gradients were often idiosyncratic, and covariation in ITV was weaker between vegetative and floral traits than within the two trait groups. [Main conclusions] Our results show that, depending on the traits considered, ITV either increased or decreased with climate stress and species richness, suggesting that both factors can constrain or enhance ITV, which might foster plant‐population persistence in stressful conditions. Given the species‐specific responses and covariation in ITV, associations can be hard to predict for traits and species not yet studied. We conclude that consideration of ITV can improve our understanding of how plants cope with stressful conditions and environmental change across spatial and biological scales., Open Access funding was provided by Ulm University under the DEAL‐agreement.

Resource limitation is a fundamental factor governing the composition and function of ecological communities. However, the role of resource supply in structuring the intestinal microbiome has not been established and represents a challenge for mammals that rely on microbial symbionts for digestion: too little supply might starve the microbiome while too much supply might starve the host. Here, we present evidence that microbiota occupy a habitat limited in total nitrogen supply within the large intestines of 30 mammal species. Furthermore, lowering dietary protein levels in mice reduced bacterial fecal concentrations. A gradient of stoichiometry along the length of the gut was consistent with the hypothesis that intestinal nitrogen limitation results from host absorption of dietary nutrients. Nitrogen availability though is also likely shaped by host-microbe interactions: levels of host-secreted nitrogen were altered in germfree mice and when bacterial loads were reduced via experimental antibiotic treatment. Single-cell spectrometry revealed that members of the phylum Bacteroidetes consumed nitrogen in the large intestine more readily than other commensal taxa. Collectively, our findings support a model where nitrogen limitation arises from preferential host utilization of dietary nutrients, and we speculate that this resource limitation could enable hosts to regulate microbial communities in the large intestine. Furthermore, commensal microbiota may have adapted to nitrogen-limited settings, suggesting why excess dietary protein has been associated with degraded gut microbial ecosystems.

Host-associated microbiota can biotransform xenobiotics, mediate health effects of chemical exposure, and play important roles in early development. Bisphenol A (BPA) is a widespread environmental chemical that has been associated with adverse endocrine and neurodevelopmental effects, some of which may be mediated by microbiota. Growing public concern over the safety of BPA has resulted in its replacement with structurally similar alternatives. In this study, we evaluated whether BPA and BPA alternatives alter microbiota and modulate secondary adverse behavioral effects in zebrafish. Zebrafish were developmentally exposed to BPA, Bisphenol AF (BPAF), Bisphenol B (BPB), Bisphenol F (BPF), or Bisphenol S (BPS). At 10 days post fertilization (dpf), toxicity assessments were completed and 16S rRNA gene sequencing was performed to evaluate potential chemical-dependent shifts in microbial community structure and predicted function. A standard light/dark behavioral assay was used to assess locomotor activity. Based on developmental toxicity assessments at 10 dpf, a range of potencies was observed: BPAF > BPB > BPF ∼ BPA > BPS. Analysis of 16S rRNA gene sequencing data showed significant concentration-dependent disruption of microbial community structure and enrichment of putative microbial functions with exposure to BPS, BPA, or BPF, but not BPB or BPAF. Interestingly, microbial disruption was inversely related to host developmental toxicity and estrogenicity. Exposure to BP analogs did not cause behavioral effects at 10 dpf. Our findings indicate that some BP analogs disrupt host microbiota early in life and demonstrate novel chemical-microbiota interactions that may add important context to current hazard identification strategies.

Watershed urbanization introduces a variety of physical, chemical, and thermal stressors to receiving streams and leads to well-documented declines in the diversity of fish and macroinverte...

Secondary succession, the postdisturbance transition of herbaceous to woody-dominated ecosystems, occurs faster at lower latitudes with important ramifications for ecosystem processes. This pattern could be driven by the direct effect of temperature on tree growth; however, an alternative mechanism is tree-herb competition, which may be more intense in more fertile northern soils. We manipulated soil fertility and herbaceous species composition in identical experiments at six sites spanning the Eastern United States (30-43° N) and monitored the growth and survival of four early successional trees. Tree seedling mass 2 years after sowing was strongly associated with site differences in mean growing season temperature, regardless of species or soil treatment. The effect of temperature was twofold: seedlings grew faster in response to warmer site temperatures, but also due to the reduction of competitive interference from the herbaceous community, which was inhibited in warmer sites. Our results suggest that increasing temperatures will promote a faster transition of fields to forests in temperate ecosystems.

Horizontal drilling and hydraulic fracturing extraction procedures have become increasingly present in Pennsylvania where the Marcellus Shale play is largely located. The potential for long-term environmental impacts to nearby headwater stream ecosystems and aquatic bacterial assemblages is still incompletely understood. Here, we perform high-throughput sequencing of the 16 S rRNA gene to characterize the bacterial community structure of water, sediment, and other environmental samples (n = 189) from 31 headwater stream sites exhibiting different histories of fracking activity in northwestern Pennsylvania over five years (2012–2016). Stream pH was identified as a main driver of bacterial changes within the streams and fracking activity acted as an environmental selector for certain members at lower taxonomic levels within stream sediment. Methanotrophic and methanogenic bacteria (i.e. Methylocystaceae, Beijerinckiaceae, and Methanobacterium) were significantly enriched in sites exhibiting Marcellus shale activity (MSA+) compared to MSA− streams. This study highlighted potential sentinel taxa associated with nascent Marcellus shale activity and some of these taxa remained as stable biomarkers across this five-year study. Identifying the presence and functionality of specific microbial consortia within fracking-impacted streams will provide a clearer understanding of the natural microbial community’s response to fracking and inform in situ remediation strategies.

Plant trait expression is shaped by filters, which can alter trait means and variances, theoretically driving species toward an "optimum" trait value for a set of environmental conditions. Recent research has highlighted the ubiquity of intraspecific variation in functional traits, which can cause plants to diverge from a hypothesized "optimum". We examined whether species occurring in "core" habitats (where they occur frequently, abundantly, and consistently) express traits that are nearer to "optimum", as captured by the community-weighted mean (CWM). We also asked whether trait variance showed signs of environmental filtering. We used cluster analysis to group plots based on environmental factors along a wet-to-dry ecotone. We used indicator species analysis to identify species with strong associations within each cluster. Trait means and variances were compared, and evidence of variance filtering was tested using a null-model approach. Trait means and trait variances respond to local-scale environmental filtering and species in core habitats were not necessarily nearer to the CWM than in other habitats. Intraspecific trait variability shows a strong signal of filtering, as variability was reduced for nearly all species and all traits compared to estimates of variability generated in the absence of environmental filtering. Our results provide strong evidence that species traits are not necessarily near "optimum" trait values in core habitats, and that trait distributions within species are strongly shaped by the environment. Future analyses should account for this divergence when calculating metrics of functional diversity, and extrapolating to ecosystem function.

Boom-bust dynamics - the rise of a population to outbreak levels, followed by a dramatic decline - have been associated with biological invasions and offered as a reason not to manage troublesome invaders. However, boom-bust dynamics rarely have been critically defined, analyzed, or interpreted. Here, we define boom-bust dynamics and provide specific suggestions for improving the application of the boom-bust concept. Boom-bust dynamics can arise from many causes, some closely associated with invasions, but others occurring across a wide range of ecological settings, especially when environmental conditions are changing rapidly. As a result, it is difficult to infer cause or predict future trajectories merely by observing the dynamic. We use tests with simulated data to show that a common metric for detecting and describing boom-bust dynamics, decline from an observed peak to a subsequent trough, tends to severely overestimate the frequency and severity of busts, and should be used cautiously if at all. We review and test other metrics that are better suited to describe boom-bust dynamics. Understanding the frequency and importance of boom-bust dynamics requires empirical studies of large, representative, long-term data sets that use clear definitions of boom-bust, appropriate analytical methods, and careful interpretations.

Background and aims Individuals with familial adenomatous polyposis (FAP) may undergo a total proctocolectomy with ileal pouch-anal anastomosis (IPAA) to surgically treat their disease. Inflammation of the ileal pouch, termed pouchitis, is uncommon in FAP patients but prevalent in patients who received IPAA for ulcerative colitis, a type of inflammatory bowel disease (IBD). Methods and results We report on two FAP siblings, living in the same household, who underwent IPAA surgery within one week of each other. Their mother also had an IPAA for FAP. One sibling developed pouchitis while his brother and mother have remained pouchitis-free. We investigated the genetic and microbial factors that might explain the development of pouchitis in the one sibling. We surveyed DNA isolated from the two brothers and their parents for NOD2 IBD risk variants by Sanger sequencing. The composition of mucosa-associated bacteria was analyzed by 16S rRNA gene sequencing on terminal ileum and rectal tissue collected at the time of surgical resection from the two brothers. The sibling with pouchitis inherited the IBD-associated risk alleles for NOD2 (rs17221417 and rs2076756) from his healthy father. Both the mother and unaffected brother lacked these variants. Microbiome sequencing of the terminal ileum and rectum found reduced levels of potentially 'beneficial' bacteria (Faecalibacterium prausnitzii, Bacteroides, and Ruminococcaceae) in the sibling with pouchitis relative to his brother. Conclusion These findings suggest that the NOD2 signaling pathway may contribute to intrinsic bacterial dysbiosis which is pre-existing and which may then predispose individuals to pouchitis after IPAA surgery.

The causes of species rarity are of critical concern because of the high extinction risk associated with rarity. Studies examining individual rare species have limited generality, whereas trait-based approaches offer a means to identify functional causes of rarity that can be applied to communities with disparate species pools. Differences in functional traits between rare and common species may be indicative of the functional causes of species rarity and may therefore be useful in crafting species conservation strategies. However, there is a conspicuous lack of studies comparing the functional traits of rare species and co-occurring common species. We measured 18 important functional traits for 19 rare and 134 common understory plant species from North Carolina's Sandhills region and compared their trait distributions to determine whether there are significant functional differences that may explain species rarity. Flowering, fire, and tissue-chemistry traits differed significantly between rare and common, co-occurring species. Differences in specific traits suggest that fire suppression has driven rarity in this system and that changes to the timing and severity of prescribed fire may improve conservation success. Our method provides a useful tool to prioritize conservation efforts in other systems based on the likelihood that rare species are functionally capable of persisting.

Many ecosystems experience drastic changes to soil nutrient availability associated with fire, but the magnitude and duration of these changes are highly variable among vegetation and fire types. In pyrogenic pine savannas across the southeastern United States, pulses of soil inorganic nitrogen (N) occur in tandem with ecosystem-scale nutrient losses from prescribed burns. Despite the importance of this management tool for restoring and maintaining fire-dependent plant communities, the contributions of different mechanisms underlying fire-associated changes to soil N availability remain unclear. Pulses of N availability following fire have been hypothesized to occur through (1) changes to microbial cycling rates and (2) direct ash deposition. Here, we document fire-associated changes to N availability across the growing season in a longleaf pine savanna in North Carolina. To differentiate between possible mechanisms driving soil N pulses, we measured net microbial cycling rates and changes to soil δ15N before and after a burn. Our findings refute both proposed mechanisms: we found no evidence for changes in microbial activity, and limited evidence that ash deposition could account for the increase in ammonium availability to more than 5–25 times background levels. Consequently, we propose a third mechanism to explain post-fire patterns of soil N availability, namely that (3) changes to plant sink strength may contribute to ephemeral increases in soil N availability, and encourage future studies to explicitly test this mechanism.

It is widely assumed that higher levels of intraspecific variability in one or more traits should allow species to persist under a wider range of environmental conditions. However, few studies have examined whether species that exhibit high variability are found in a wider range of environmental conditions, and whether variability increases the ability of a species to adapt to prevailing ecological gradients. We used four plant functional traits, specific leaf area (SLA), leaf dry matter content (LDMC), leaf carbon to nitrogen ratio (C:N) and maximum plant height in 49 species across a strong environmental gradient to answer three questions: 1) is there evidence for ‘high-variability’ species (that is, species which show high variability in multiple traits, simultaneously)? 2) are species with more variable traits present across a wider range of environmental conditions than less variable species? And 3) whether more variable species show better trait-environment matching to the prevailing abiotic (soil moisture) gradient at the site? We found little evidence for a ‘high-variability’ species. Variability was correlated for two leaf traits, SLA and LDMC, while variability in leaf traits and plant height were not correlated. We found little evidence that more variable species were present in more diverse conditions: only variation in SLA was correlated with a wider ecological niche breadth. For plant traits along the soil-moisture gradient, higher variability led to better trait-environment matching in half of measured traits. Overall, we found little support for the existence of ‘high-variability’ species, but that variability in SLA is correlated with a wider ecological breadth. We also found evidence that variation in traits can improve trait-environment matching, a relationship which may facilitate our understanding ecological breadth along prevailing gradients, and community assembly on the basis of traits. This article is protected by copyright. All rights reserved.

Rare species reintroductions are an increasingly common conservation strategy, but often result in poor survival of reintroduced individuals. Reintroduction sites are chosen primarily based on historical occupancy and/or abiotic properties of the site, with much less consideration given to properties of the larger biotic community. However, ecological niche theory suggests that the ability to coexist with other species is determined in part by the degree of functional similarity between species. The degree to which functional similarity affects the survival of reintroduced plants is poorly understood, but has important implications for the allocation of limited conservation resources. We collected a suite of abiotic, biotic, and functional trait variables centered on outplanted individuals from four reintroduced rare plant species and used logistic regression and model selection to assess their influence on individual survival. We show that higher functional similarity between reintroduced individuals and the local community, measured by differences between their multivariate functional traits and the community-weighted mean traits of their immediate neighbors, increases survival and is a stronger predictor of survival than local variation in abiotic factors, suggesting that the functional composition of the biotic community should be incorporated into site selection to improve reintroduction success.

SummaryInfants are at a high risk of acquiring infections caused by antibiotic resistant bacterial strains. Antibiotic resistance gene (ARG) load is typically higher in newborns than in adults, but it is unknown which factors besides antibiotic treatment affect the load. Our study demonstrates that inclusion of any formula in the newborn diet causes shifts in microbial community composition that result in higher ARG loads in formula-fed infants compared to infants not fed formula. The effect of formula was especially strong in premature newborns and newborns treated with antibiotics. Interestingly, antibiotics alone without formula did not have a detectable impact on the ARG load of the newborn gut. We also observed that formula-fed infants had enriched numbers of pathogenic species and were depleted in typical infant gut species such as Bifidobacterium bifidum. The results suggest infant feeding choices should include assessment of risks associated with elevated ARG abundance.

Seed gut passage times, the time from ingestion to defecation, and frugivore movement patterns determine patterns of seed deposition across the landscape and are thus crucial parameters to quantify in wild populations. Recent advancements in satellite and telemetry technologies mean that animal movement patterns are readily quantifiable in increasingly high resolution. However, data on wild frugivore gut passage times are scarce to non-existent due to the difficulty of monitoring seed ingestion and defecation in natural habitats; therefore, GPT estimates are often extrapolated from captive species whose diets and activity patterns may have limited transferability to free-ranging populations. Here we develop, trial and deploy a suite of model seeds to address this shortfall in wild African forest elephants Loxodonta cyclotis – one of the most effective seed dispersers in the tropics. We use a combination of ‘active’ seed mimics, which indirectly measure gut passage through recording temperature fluctuations, and ‘passive’ seed mimics, which serve to mark the point of defecation to allow gut passage estimation from time-stamped GPS collar data. In doing so, we present the first ever GPT estimates from wild forest elephants: mean = 39.8 h (min = 16.6 h; max = 113.7 h). The estimates were derived exclusively from passive seed mimics (plastic beads and modified native seeds) as all active seed mimics were rejected by the focal elephant. The methods described are translatable to other free-ranging, GPS-collared, species and if widely adopted, will begin to address the current gap in our understanding of seed dispersal by wild frugivores.

Bacterial swarming is a conserved and distinct form of bacterial motility that is often regulated differently than biofilm communities. While bacterial biofilms are associated with pathogenesis and pathobiology of human diseases, there are very few examples of swarming behaviors that uniquely define or align with human pathophysiology. Here we report that bacterial swarmers are associated with protection against intestinal inflammation in a murine model of acute colitis. Using feces in soft-agar plate assay, we showed bacterial spreading harboring swarmers, is highly predictive of the presence of intestinal stress in mice, pigs, and humans. From murine feces, we isolated a novel Enterobacter swarming strain, SM3, which demonstrated significant protection from intestinal inflammation when compared to its swarming deficient but swimming competent transposon mutants in a DSS-induced intestinal inflammation model of mice. Known commensal swarmers also protected against intestinal inflammation when compared to swarming deficient isogenic mutants. When treated with SM3, its anti-inflammatory properties paralleled a significant reduction of luminal oxygen concentration in colitic mice as observed in real time using a microsensor probe. This led to a favorable anaerobic environment conducive to the growth of beneficial anaerobes as demonstrated by 16S profiling of feces. This work identifies a new paradigm in which intestinal stress, specifically inflammation, allows for the emergence of swarming bacteria, which in turn can protect and heal from intestinal inflammation.

Our data suggest a potential role for fungi in the most common nosocomial bacterial infection in the United States, introducing the concept of a transkingdom interaction between bacteria and fungi in this disease. We also provide the first direct measure of microbial community function in Clostridioides difficile infection using patient-derived tissue samples, revealing antibiotic-independent mechanisms by which C. difficile infection may resist a return to a healthy gut microbiome., There has been no prior application of matched metagenomics and metatranscriptomics in Clostridioides difficile infection (CDI) evaluating the role of fungi in CDI or identifying community functions that contribute to the development of this disease. We collected diarrheal stools from 49 inpatients (18 of whom tested positive for CDI) under stringent inclusion criteria. We utilized a tiered sequencing approach to identify enriched bacterial and fungal taxa, using 16S and internal transcribed spacer (ITS) rRNA gene amplicon sequencing, with matched metagenomics and metatranscriptomics performed on a subset of the population. Distinct bacterial and fungal compositions distinguished CDI-positive and -negative patients, with the greatest differentiation between the cohorts observed based on bacterial metatranscriptomics. Bipartite network analyses demonstrated that Aspergillus and Penicillium taxa shared a strong positive relationship in CDI patients and together formed negative cooccurring relationships with several bacterial taxa, including the Oscillospira, Comamonadaceae, Microbacteriaceae, and Cytophagaceae. Metatranscriptomics revealed enriched pathways in CDI patients associated with biofilm production primarily driven by Escherichia coli and Pseudomonas, quorum-sensing proteins, and two-component systems related to functions such as osmotic regulation, linoleic acid metabolism, and flagellar assembly. Differential expression of functional pathways unveiled a mechanism by which the causal dysbiosis of CDI may self-perpetuate, potentially contributing to treatment failures. We propose that CDI has a distinct fungus-associated bacteriome, and this first description of metatranscriptomics in human subjects with CDI demonstrates that inflammation, osmotic changes, and biofilm production are key elements of CDI pathophysiology. IMPORTANCE Our data suggest a potential role for fungi in the most common nosocomial bacterial infection in the United States, introducing the concept of a transkingdom interaction between bacteria and fungi in this disease. We also provide the first direct measure of microbial community function in Clostridioides difficile infection using patient-derived tissue samples, revealing antibiotic-independent mechanisms by which C. difficile infection may resist a return to a healthy gut microbiome.

Arsenic is ubiquitous in nature, highly toxic, and is particularly abundant in Southern Asia. While many studies have focused on areas like Bangladesh and West Bengal, India, disadvantaged regions within Nepal have also suffered from arsenic contamination levels, with wells and other water sources possessing arsenic contamination over the recommended WHO and EPA limit of 10 μg/L, some wells reporting levels as high as 500 μg/L. Despite the region's pronounced arsenic concentrations within community water sources, few investigations have been conducted to understand the impact of arsenic contamination on host gut microbiota health. This study aims to examine differential arsenic exposure on the gut microbiome structure within two disadvantaged communities in southern Nepal. Fecal samples (n = 42) were collected from members of the Mahuawa (n = 20) and Ghanashyampur (n = 22) communities in southern Nepal. The 16S rRNA gene was amplified from fecal samples using Illumina-tag PCR and subject to high-throughput sequencing to generate the bacterial community structure of each sample. Bioinformatics analysis and multivariate statistics were conducted to identify if specific fecal bacterial assemblages and predicted functions were correlated with urine arsenic concentration. Our results revealed unique assemblages of arsenic volatilizing and pathogenic bacteria positively correlated with increased arsenic concentration in individuals within the two respective communities. Additionally, we observed that commensal gut bacteria negatively correlated with increased arsenic concentration in the two respective communities. Our study has revealed that arsenic poses a broader human health risk than was previously known. It is influential in shaping the gut microbiome through its enrichment of arsenic volatilizing and pathogenic bacteria and subsequent depletion of gut commensals. This aspect of arsenic has the potential to debilitate healthy humans by contributing to disorders like heart and liver cancers and diabetes, and it has already been shown to contribute to serious diseases and disorders, including skin lesions, gangrene and several types of skin, renal, lung, and liver cancers in disadvantaged areas of the world like Nepal., Microbiology, Public Health; Gut microbiome; Arsenic; Well water; Nepal

Background and aims Coastal plant communities globally are highly vulnerable to future sea-level rise and storm damage, but the extent to which these habitats are affected by the various environmental perturbations associated with chronic salinization remains unclear. In this study, we examine the relationship between North Carolina wetland tree community composition and basal area change and indicators of salinization such as soil salt ion content and elevation. Methods We surveyed 34 forest plots in forested, freshwater wetlands across the Albemarle-Pamlico Peninsula. A subset of our study sites had been sampled during the previous decade as part of the Carolina Vegetation Survey, enabling us to investigate the environmental effects on current community structure, and community change over time. Key results Multi-variate (ordination) analysis and linear regression models of tree community composition revealed that elevation and soil salt content were correlated with changes in total site tree basal area. Shifts in tree community composition were, however, only weakly correlated with indicators of salinization, specifically elevation, soil sulphate and sodium, but not chloride. While the majority of plots experienced gains in basal area over the past decade, consistent with secondary succession, sites with high soil salt content or low elevation experienced basal area (biomass) loss during the same period. Conclusions The key factors associated with chronic saltwater intrusion (soil ion content) likely explain recent changes in tree biomass, and potential shifts in community composition in low-elevation sites along the North Carolina coast. Not only is it probable that other coastal forest ecosystems worldwide will experience similar stressors and shifts in community biomass and structure as sea levels rise, but the ability of these habitats to deliver key ecosystem services like carbon sequestration and flood defence will be compromised as a result.