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Self-sustaining vegetation in metal-contaminated areas is essential for rebuilding ecological resilience and community stability in degraded lands. Metal-tolerant plants originating from contaminated post-mining areas may hold the key to successful plant establishment and growth. Yet, little is known about the impact of metal toxicity on reproductive strategies, metal accumulation, and allocation patterns at the seed stage. Our research focused on the metal tolerant Atriplex lentiformis. Specifically, we examined the effects of toxic metal(loid) concentration in soils on variability in its reproductive strategies, including germination patterns, elemental uptake, and allocation within the seeds. We employed advanced imaging techniques like synchrotron X-ray fluorescence microscopy (2D scans and 3D tomograms) combined with inductively coupled plasma mass spectrometry to reveal significant differences in metal(loid) concentration and distribution within the seed structures of A. lentiformis from contrasting habitats. Exclusive Zn hotspots of high concentrations were found in the seeds of the metallicolous accession, primarily in the sensitive tissues of shoot apical meristems and root zones of the seed embryos. Our findings offer novel insights into phenotypic variability and metal tolerance and accumulation in plants from extreme environments. This knowledge can be applied to enhance plant survival and performance in land restoration efforts., (© The Author(s) 2024. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

Successful phytoremediation of acidic metal-contaminated mine tailings requires amendments to condition tailings properties prior to plant establishment. This conditioning process is complex and includes multiple changes in tailings bio-physico-chemical properties. The objective of this project is to identify relationships between tailings properties, the soil microbiome, and plant stress response genes during growth of Atriplex lentiformis in compost-amended (10 %, 15 %, 20 % w/w) mine tailings. Analyses include RNA-Seq for plant root gene expression, 16S rRNA amplicon sequencing for bacterial/archaeal communities, metal concentrations in both tailings and plant organs, and phenotypic measures of plant stress. Zn accumulation in A. lentiformis leaves varied with compost levels and was the highest in the intermediate treatment (15 %, TC15). Microbial analysis identified Alicyclobacillus, Hydrotalea, and Pseudolabrys taxa with the highest relative abundance in TC15, and these taxa were strongly associated with Zn accumulation. Furthermore, we identified 190 root genes with significant gene expression changes. These root genes were associated with different pathways including, abscisic acid and auxin signaling, defense responses, ion channels, metal ion binding, oxidative stress, transcription regulation, and transmembrane transport. However, root gene expression changes were not driven by the increasing levels of compost. For example, there were 15 genes that were up-regulated in TC15, whereas 106 genes were down-regulated in TC15. The variables analyzed explained 86 % of the variance in Zn accumulation in A. lentiformis leaves. Importantly, Zn accumulation was driven by Zn shoot concentrations, leaf stress symptoms, plant root genes, and microbial taxa. Therefore, our results suggest there are strong plant-microbiome associations that drive Zn accumulation in A. lentiformis and different plant gene pathways are involved in alleviating varying levels of metal stress. Future work is needed to gain a mechanistic understanding of these plant-microbiome interactions to optimize phytoremediation strategies as they will govern the success or failure of the revegetation process., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

The exceptionally long and protracted aridity in the Atacama Desert (AD), Chile, provides an extreme, terrestrial ecosystem that is ideal for studying microbial community dynamics under hyperarid conditions. Our aim was to characterize the temporal response of hyperarid soil AD microbial communities to ex situ simulated rainfall (5% g water/g dry soil for 4 weeks) without nutrient amendment. We conducted replicated microcosm experiments with surface soils from two previously well-characterized AD hyperarid locations near Yungay at 1242 and 1609 masl (YUN1242 and YUN1609) with distinct microbial community compositions and average soil relative humidity levels of 21 and 17%, respectively. The bacterial and archaeal response to soil wetting was evaluated by 16S rRNA gene qPCR, and amplicon sequencing. Initial YUN1242 bacterial and archaeal 16S rRNA gene copy numbers were significantly higher than for YUN1609. Over the next 4 weeks, qPCR results showed significant increases in viable bacterial abundance, whereas archaeal abundance decreased. Both communities were dominated by 10 prokaryotic phyla (Actinobacteriota, Proteobacteria, Chloroflexota, Gemmatimonadota, Firmicutes, Bacteroidota, Planctomycetota, Nitrospirota, Cyanobacteriota, and Crenarchaeota) but there were significant site differences in the relative abundances of Gemmatimonadota and Chloroflexota, and specific actinobacterial orders. The response to simulated rainfall was distinct for the two communities. The actinobacterial taxa in the YUN1242 community showed rapid changes while the same taxa in the YUN1609 community remained relatively stable until day 30. Analysis of inferred function of the YUN1242 microbiome response implied an increase in the relative abundance of known spore-forming taxa with the capacity for mixotrophy at the expense of more oligotrophic taxa, whereas the YUN1609 community retained a stable profile of oligotrophic, facultative chemolithoautotrophic and mixotrophic taxa. These results indicate that bacterial communities in extreme hyperarid soils have the capacity for growth in response to simulated rainfall; however, historic variations in long-term hyperaridity exposure produce communities with distinct putative metabolic capacities., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Demergasso, Neilson, Tebes-Cayo, Véliz, Ayma, Laubitz, Barberán, Chong-Díaz and Maier.)

Critical to the environmental sustainability of hard rock mining is the reclamation of disturbed lands following mine closure through revegetation. Improved understanding of associations between above- and belowground processes that characterize successful plant establishment is critical to the implementation of more efficient revegetation strategies for nutrient-poor mine waste materials. The specific objective of this five-year temporal study was to identify progressive biotic and abiotic indicators of primary soil development on mine waste rock (WR) on a slope hydroseeded with native plant species and to quantify comparative effects of plant lifeform on soil development. Aboveground plant diversity and belowground substrate properties were measured annually at 67 m intervals along transects following the slope contour. Seeded WR was compared to unseeded WR and the adjacent native ecosystem. A temporal increase in WR microbial biomass was observed in seeded WR relative to unseeded areas. Microbial community analysis found the unseeded WR to be defined by oligotrophic microbes, whereas targeted grass and shrub root zones samples demonstrated significant increases in specific cellulose and lignin degrading and N-cycling phylotypes. More extensive chemical and biological fertility development was observed in shrub root zones relative to grass. Ten chemical and biological indicators increased significantly in shrub WR relative to unseeded WR, whereas grass WR was only enriched in bacterial 16S rRNA gene copy number/g substrate and bacterial/archaeal and fungal diversity. In addition, the shrub root zone had significantly higher nitrogen-cycling potential than grass root zones or unseeded WR. Thus, both grasses and shrubs improve belowground WR development; however, shrub establishment had greater fertility outcomes. Concurrent belowground fertility development is critical to sustainable plant establishment. Coupled evaluation of above- and belowground metrics provides an improved quantitative assessment of revegetation progress and a valuable tool to guide management decisions., Competing Interests: Declaration of interests The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Jesse Dillon is the owner of Cedar Creek Associates, an ecological consulting firm with contracts with the mining industry focused on environmental permitting, regulatory compliance, and closure. Research for this manuscript was conducted at a copper mine that is a contributing member to the University of Arizona Center for Environmentally Sustainable Mining Industry-Academic Revegetation Research Cooperative as described in the Acknowledgements.

Arsenic is ubiquitous in soil and water environments and is consistently at the top of the Agency for Toxic Substances Disease Registry (ATSDR) substance priority list. It has been shown to induce toxicity even at low levels of exposure. One of the major routes of exposure to arsenic is through drinking water. This review presents current information related to the distribution of arsenic in the environment, the resultant impacts on human health, especially related to diabetes, which is one of the most prevalent chronic diseases, regulation of arsenic in drinking water, and approaches for treatment of arsenic in drinking water for both public utilities and private wells. Taken together, this information points out the existing challenges to understanding both the complex health impacts of arsenic and to implementing the treatment strategies needed to effectively reduce arsenic exposure at different scales., Competing Interests: Conflicts of Interest: The authors declare no conflict of interest.

Identifying and exploiting cost-effective and green methods of metal recovery from natural and contaminated aqueous systems is widely recognized as necessary to supplement the supply of critical elements, decrease the environmental impacts associated with hardrock mining, and remediate metal-contaminated waters. This research examines a novel approach based on rhamnolipid-facilitated chemical precipitation of metals. Three techniques were assessed to remove the rhamnolipid:metal complex from solution: mixing only, and mixing following by filtration or centrifugation. Recent advances in the ability to synthetically produce rhamnolipid surfactants allowed investigation of a variety of rhamnolipid structures. Rhamnolipids differing in the length and number of hydrophobic tails were assessed to remove Pb, La, and Mg from single metal solutions. In general, removal increased with increased rhamnolipid hydrophobicity and with the addition of an active removal step (filtration or centrifugation). Filtration removed up to 96% of all metals while centrifugation removed up to 97% for Pb and La and 60% for Mg. Results suggest tailoring the rhamnolipid structure and removal methods may enable selective metal removal to achieve specific outcomes. Future studies in mixed-metal and real-world solutions will be needed to confirm the viability of these techniques in complex systems., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: David E. Hogan reports equipment, drugs, or supplies was provided by GlycoSurf, Inc. Raina M. Maier reports equipment, drugs, or supplies was provided by GlycoSurf, Inc. Raina M. Maier reports a relationship with GlycoSurf, Inc. that includes: board membership and equity or stocks. David E. Hogan reports a relationship with GlycoSurf, Inc. that includes: employment. David E. Hogan has patent Separation of Metal Ions from a Sample Using Glycolipids pending to Arizona Board of Regents of University of Arizona. Raina M. Maier has patent Separation of Metal Ions from a Sample Using Glycolipids pending to Arizona Board of Regents of University of Arizona., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Understanding the temporal effects of organic matter input and water influx on metal lability and translocation is critical to evaluate the success of the phytostabilization of metalliferous mine tailings. Trends of metal lability, e.g., V, Cr, Mn, Co, Ni, Cu, Zn, and Pb, were investigated for three years following a direct-planting phytostabilization trial at a Superfund mine tailings site in semi-arid central Arizona, USA. Unamended tailings were characterized by high concentrations (mmol kg -1 ) of Fe (2100), S (3100), As (41), Zn (39), and Pb (11), where As and Pb greatly exceeded non-residential soil remediation levels established by Arizona. Phytostabilization treatments included a no-compost control, 100 g kg -1 compost with seed, and 200 g kg -1 compost with and without seed to the top 20 cm of the tailings profile. All plots received supplemental irrigation, effectively doubling the mean annual precipitation. Tailings cores up to 90 cm were Collected at the time of planting and every summer for 3 years. The cores were sub-sectioned at 20 cm increments and analyzed via total digestion and an operationally defined sequential extraction for elemental analysis and the calculation of a mass transfer coefficient normalized to Ti as an assigned immobile element. The results indicate that Pb was recalcitrant and relatively immobile in the tailings environment for both the uncomposted control and composted treatments with a maximum variation in the total concentration of 9-14 mmol kg -1 among all samples. Metal lability and translocation above the redox boundary ( ca . 30 cm depth) was governed by acid generation, where surficial pH was measured as low as 2.7 ± 0.1 in year three and strongly correlated with the increased lability of Mn, Co, Ni, Cu, and Zn. There was no significant pH effect on the lability of V, Cr, or Pb. Translocation to depths was greatest for Mn and Co; however, Zn, Ni, Cr, and Cu were also mobilized. The addition of organic matter enhanced the mobilization of Cr from the near surface to 40-60 cm depth (pH > 6) over the three-year phytostabilization study compared to the control. The increased enrichment of some metals at 60-90 cm indicates that the long-term monitoring of elemental translocation is necessary to assess the efficacy of phytostabilization to contain subsurface metal contaminants and thereby protect the surrounding community from exposure., Competing Interests: Conflicts of Interest: All authors have read and agreed to the published version of the manuscript.

Human culture, biology, and health were shaped dramatically by the onset of agriculture ∼12,000 y B.P. This shift is hypothesized to have resulted in increased individual fitness and population growth as evidenced by archaeological and population genomic data alongside a decline in physiological health as inferred from skeletal remains. Here, we consider osteological and ancient DNA data from the same prehistoric individuals to study human stature variation as a proxy for health across a transition to agriculture. Specifically, we compared “predicted” genetic contributions to height from paleogenomic data and “achieved” adult osteological height estimated from long bone measurements for 167 individuals across Europe spanning the Upper Paleolithic to Iron Age (∼38,000 to 2,400 B.P.). We found that individuals from the Neolithic were shorter than expected (given their individual polygenic height scores) by an average of −3.82 cm relative to individuals from the Upper Paleolithic and Mesolithic (P = 0.040) and −2.21 cm shorter relative to post-Neolithic individuals (P = 0.068), with osteological vs. expected stature steadily increasing across the Copper (+1.95 cm relative to the Neolithic), Bronze (+2.70 cm), and Iron (+3.27 cm) Ages. These results were attenuated when we additionally accounted for genome-wide genetic ancestry variation: for example, with Neolithic individuals −2.82 cm shorter than expected on average relative to pre-Neolithic individuals (P = 0.120). We also incorporated observations of paleopathological indicators of nonspecific stress that can persist from childhood to adulthood in skeletal remains into our model. Overall, our work highlights the potential of integrating disparate datasets to explore proxies of health in prehistory.

Soil contamination with trace metal(loid) elements (TME) is a global concern. This has focused interest on TME-tolerant plants, some of which can hyperaccumulate extraordinary amounts of TME into above-ground tissues, for potential treatment of these soils. However, intra-species variability in TME hyperaccumulation is not yet sufficiently understood to fully harness this potential. Particularly, little is known about the rhizosphere microbial communities associated with hyperaccumulating plants and whether or not they facilitate TME uptake. The aim of this study is to characterize the diversity and structure of Arabidopsis halleri rhizosphere-influenced and background (i.e., non-Arabidopsis) soil microbial communities in four plant populations with contrasting Zn and Cd hyperaccumulation traits, two each from contaminated and uncontaminated sites. Microbial community properties were assessed along with geographic location, climate, abiotic soil properties, and plant parameters to explain variation in Zn and Cd hyperaccumulation. Site type (TME-contaminated vs. uncontaminated) and location explained 44% of bacterial/archaeal and 28% of fungal community variability. A linear discriminant effect size (LEfSe) analysis identified a greater number of taxa defining rhizosphere microbial communities than associated background soils. Further, in TME-contaminated soils, the number of rhizosphere-defining taxa was 6-fold greater than in the background soils. In contrast, the corresponding ratio for uncontaminated sites, was 3 and 1.6 for bacteria/archaea and fungi, respectively. The variables analyzed explained 71% and 76% of the variance in Zn and Cd hyperaccumulation, respectively; however, each hyperaccumulation pattern was associated with different variables. A. halleri rhizosphere fungal richness and diversity associated most strongly with Zn hyperaccumulation, whereas soil Cd and Zn bioavailability had the strongest associations with Cd hyperaccumulation. Our results indicate strong associations between A. halleri TME hyperaccumulation and rhizosphere microbial community properties, a finding that needs to be further explored to optimize phytoremediation technology that is based on hyperaccumulation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Mining of uranium for defense-related purposes has left a substantial legacy of pollution that threatens human and environmental health. Contaminated waters in the arid southwest are of particular concern, as water resource demand and water scarcity issues become more pronounced. The development of remediation strategies to treat uranium impacted waters will become increasingly vital to meet future water needs. Ion flotation is one technology with the potential to address legacy uranium contamination. The green biosurfactant rhamnolipid has been shown to bind uranium and act as an effective collector in ion flotation. In this study, uranium contaminated groundwater (∼440 μg L -1 U) from the Monument Valley processing site in northeast Arizona was used as a model solution to test the uranium removal efficacy of ion flotation with biosynthetic (bio-mRL) and three synthetic monorhamnolipids with varying hydrophobic chain lengths: Rha-C10-C10, Rha-C12-C12, and Rha-C14-C14. At the groundwater's native pH 8, and at an adjusted pH 7, no uranium was removed from solution by any collector. However, at pH 6.5 bio-mRL and Rha-C10-C10 removed 239.2 μg L -1 and 242.4 μg L -1 of uranium, respectively. By further decreasing the pH to 5.5, bio-mRL was able to reduce the uranium concentration to near or below the Environmental Protection Agency maximum contaminant level of 30 μg L -1 . For the Rha-C12-C12 and Rha-C14-C14 collector ligands, decreasing the pH to 7 or below reduced the foam stability and quantity, such that these collectors were not suitable for treating this groundwater. To contextualize the results, a geochemical analysis of the groundwater was conducted, and a consideration of uranium speciation is described. Based on this study, the efficacy of monorhamnolipid-based ion flotation in real world groundwater has been demonstrated with suitable solution conditions and collectors identified., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Microbial communities in incipient soil systems serve as the only biotic force shaping landscape evolution. However, the underlying ecological forces shaping microbial community structure and function are inadequately understood. We used amplicon sequencing to determine microbial taxonomic assembly and metagenome sequencing to evaluate microbial functional assembly in incipient basaltic soil subjected to precipitation. Community composition was stratified with soil depth in the pre-precipitation samples, with surficial communities maintaining their distinct structure and diversity after precipitation, while the deeper soil samples appeared to become more uniform. The structural community assembly remained deterministic in pre- and post-precipitation periods, with homogenous selection being dominant. Metagenome analysis revealed that carbon and nitrogen functional potential was assembled stochastically. Sub-populations putatively involved in the nitrogen cycle and carbon fixation experienced counteracting assembly pressures at the deepest depths, suggesting the communities may functionally assemble to respond to short-term environmental fluctuations and impact the landscape-scale response to perturbations. We propose that contrasting assembly forces impact microbial structure and potential function in an incipient landscape; in situ landscape characteristics (here homogenous parent material) drive community structure assembly, while short-term environmental fluctuations (here precipitation) shape environmental variations that are random in the soil depth profile and drive stochastic sub-population functional dynamics., Competing Interests: TV is currently employed by Accenture GmbH. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Sengupta, Volkmann, Danczak, Stegen, Dontsova, Abramson, Bugaj, Volk, Matos, Meira-Neto, Barberán, Neilson, Maier, Chorover, Troch and Meredith.)

Critical metals, identified from supply, demand, imports, and market factors, include rare earth elements (REE), platinum group metals, precious metals, and other valuable metals such as lithium, cobalt, nickel, and uranium. Extraction of metals from U.S. saline aqueous, emphasizing saline, sources is explored as an alternative to hardrock ore mining. Potential aqueous sources include seawater, desalination brines, oil-and-gas produced waters, geothermal aquifers, and acid mine drainage, among others. A feasibility assessment reveals opportunities for recovery of lithium, strontium, magnesium, and several REE from select sources, in quantities significant for U.S. manufacturing and for reduction of U.S. reliance on international supply chains. This is a conservative assessment given that water quality data are lacking for a significant number of critical metals in certain sources. The technology landscape for extraction and recovery of critical metals from aqueous sources is explored, identifying relevant processes along with knowledge gaps. Our analysis indicates that aqueous mining would result in much lower environmental impacts on water, air, and land than ore mining. Preliminary assessments of the economics and energy consumption of recovery show potential for recovery of critical metals.

Environmental contamination is a fundamental determinant of health and well-being, and when the environment is compromised, vulnerabilities are generated. The complex challenges associated with environmental health and food security are influenced by current and emerging political, social, economic, and environmental contexts. To solve these "wicked" dilemmas, disparate public health surveillance efforts are conducted by local, state, and federal agencies. More recently, citizen/community science (CS) monitoring efforts are providing site-specific data. One of the biggest challenges in using these government datasets, let alone incorporating CS data, for a holistic assessment of environmental exposure is data management and interoperability. To facilitate a more holistic perspective and approach to solution generation, we have developed a method to provide a common data model that will allow environmental health researchers working at different scales and research domains to exchange data and ask new questions. We anticipate that this method will help to address environmental health disparities, which are unjust and avoidable, while ensuring CS datasets are ethically integrated to achieve environmental justice. Specifically, we used a transdisciplinary research framework to develop a methodology to integrate CS data with existing governmental environmental monitoring and social attribute data (vulnerability and resilience variables) that span across 10 different federal and state agencies. A key challenge in integrating such different datasets is the lack of widely adopted ontologies for vulnerability and resiliency factors. In addition to following the best practice of submitting new term requests to existing ontologies to fill gaps, we have also created an application ontology, the Superfund Research Project Data Interface Ontology (SRPDIO)., Competing Interests: Conflict of Interest: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

The overwhelming taxonomic diversity and metabolic complexity of microorganisms can be simplified by a life-history classification; copiotrophs grow faster and rely on resource availability, whereas oligotrophs efficiently exploit resource at the expense of growth rate. Here, we hypothesize that community-level traits inferred from metagenomic data can distinguish copiotrophic and oligotrophic microbial communities. Moreover, we hypothesize that oligotrophic microbial communities harbor more unannotated genes. To test these hypotheses, we conducted metagenomic analyses of soil samples collected from copiotrophic vegetated areas and from oligotrophic bare ground devoid of vegetation in an arid-hyperarid region of the Sonoran Desert, Arizona, USA. Results supported our hypotheses, as we found that multiple ecologically informed life-history traits including average 16S ribosomal RNA gene copy number, codon usage bias in ribosomal genes and predicted maximum growth rate were higher for microbial communities in vegetated than bare soils, and that oligotrophic microbial communities in bare soils harbored a higher proportion of genes that are unavailable in public reference databases. Collectively, our work demonstrates that life-history traits can distill complex microbial communities into ecologically coherent units and highlights that oligotrophic microbial communities serve as a rich source of novel functions.

Increasing temperatures and drought in desert ecosystems are predicted to cause decreased vegetation density combined with barren ground expansion. It remains unclear how nutrient availability, microbial diversity, and the associated functional capacity vary between vegetated-canopy and gap soils. The specific aim of this study was to characterize canopy vs gap microsite effect on soil microbial diversity, the capacity of gap soils to serve as a canopy-soil microbial reservoir, nitrogen (N)-mineralization genetic potential ( ureC gene abundance) and urease enzyme activity, and microbial-nutrient pool associations in four arid-hyperarid geolocations of the western Sonoran Desert, Arizona (USA). Microsite combined with geolocation explained 57% and 45.8% of the observed variation in bacterial/archaeal and fungal community composition, respectively. A core microbiome of amplicon sequence variants was shared between the canopy and gap soil communities; however, canopy-soils included abundant taxa that were not present in associated gap communities, thereby suggesting that these taxa cannot be sourced from the associated gap soils. Linear mixed-effects models showed that canopy-soils have significantly higher microbial richness, nutrient content, and organic N-mineralization genetic and functional capacity. Furthermore, ureC gene abundance was detected in all samples suggesting that ureC is a relevant indicator of N-mineralization in deserts. Additionally, novel phylogenetic associations were observed for ureC with the majority belonging to Actinobacteria and uncharacterized bacteria. Thus, key N-mineralization functional capacity is associated with a dominant desert phylum. Overall, these results suggest that lower microbial diversity and functional capacity in gap soils may impact ecosystem sustainability as aridity drives open-space expansion in deserts., (Copyright © 2020 American Society for Microbiology.)

Particulate and dissolved metal(loid) release from mine tailings is of concern in (semi-) arid environments where tailings can remain barren of vegetation for decades and, therefore, become highly susceptible to dispersion by wind and water. Erosive weathering of metalliferous tailings can lead to arsenic contamination of adjacent ecosystems and increased risk to public health. Management via phytostabilization with the establishment of a vegetative cap using organic amendments to enhance plant growth has been employed to reduce both physical erosion and leaching. However, prior research suggests that addition of organic matter into the oxic weathering zone of sulfide tailings has the potential to promote the mobilization of arsenate. Therefore, the objective of the current work was to assess the impacts of phytostabilization on the molecular-scale mechanisms controlling arsenic speciation and lability. These impacts, which remain poorly understood, limit our ability to mitigate environmental and human health risks. Here we report on subsurface biogeochemical transformations of arsenic and iron from a three-year phytostabilization field study conducted at a Superfund site in Arizona, USA. Legacy pyritic tailings at this site contain up to 3 g kg -1 arsenic originating from arsenopyrite that has undergone oxidation to form arsenate-ferrihydrite complexes in the top 1 m. Tailings were amended in the top 20 cm with 100, 150, or 200 g kg -1 (300-600 T ha -1 ) of composted organic matter and seeded with native halotolerant plant species. Treatments and an unamended control received irrigation of 360 ± 30 mm y -1 in addition to 250 ± 160 mm y -1 of precipitation. Cores to 1 m depth were collected annually for three years and sectioned into 20 cm increments for analysis by synchrotron iron and arsenic X-ray absorption spectroscopy (XAS) coupled with quantitative wet chemical and mass balance methods. Results revealed that > 80% of arsenic exists in ammonium oxalate-extractable and non-extractable phases, including dominantly ferrihydrite and jarosite. Arsenic release during arsenopyrite oxidation resulted in both downward translocation and As (V) attenuation by stable Fe (III) (oxyhydr)oxide and Fe (III) (hydroxy)sulfate minerals over time, highlighting the need for sampling at multiple depths and time points for accurate interpretation of arsenic speciation, lability, and translocation in weathering profiles. Less than 1% of total arsenic was highly-labile, i.e. water-extractable, from all treatments, depths, and years, and more than 99% of arsenate released by arsenopyrite weathering was attenuated by association with secondary minerals. Although downward translocation of both arsenic and iron was detected during phytostabilization by temporal enrichment analysis, a similar trend was measured for the uncomposted control, indicating that organic amendment associated with phytostabilization practices did not significantly increase arsenic mobilization over non-amended controls.

In 2014, almost 16 million tons of surfactants were used globally for cleaning and industrial applications. As a result, massive quantities disperse into environmental compartments every day. There is great market interest in developing highly biodegradable, less-toxic, and renewable alternatives to currently used petroleum-based surfactants. Glycolipid surfactants, composed of a sugar head-group and lipid tail, are effective surfactants and emulsifiers with a high tolerance to electrolytes and are easily tailored to address specific needs. The green synthesis and surfactant characteristics of a suite of cellobiosides and melibiosides were recently described. The biodegradability and toxicity of 1°-alkyl-O-cellobiosides, 2°-alkyl-O-cellobiosides, and 1°-alkyl-O-melibiosides with straight-chain alkyl tails of 8, 10, and 12 are reported in this study. Biodegradability was assessed by quantifying mineralization (CO 2 evolution). All of the glycosides were inherently biodegradable and most were readily biodegradable according to OECD and EPA definitions. The Microtox acute toxicity assay showed both chain length and head group had significant effects on toxicity, but most of the molecules were practically non-toxic according to EPA definitions with EC 50 values > 100 mg L -1 . Cytotoxicity to human lung (H1299) and keratinocyte cell lines (HaCaT) was measured by xCELLigence and MTS assays. Cytotoxicity values were comparable to similar glycosides previously reported. IC 50 values were determined but, in general, exceeded surfactant concentrations that are found in the environment. These data demonstrate the promising nature of these molecules as green alternatives to petrochemical surfactants.

The relative contributions of genetics and environment to temporal and geographic variation in human height remain largely unknown. Ancient DNA has identified changes in genetic ancestry over time, but it is not clear whether those changes in ancestry are associated with changes in height. Here, we directly test whether changes over the past 38,000 y in European height predicted using DNA from 1,071 ancient individuals are consistent with changes observed in 1,159 skeletal remains from comparable populations. We show that the observed decrease in height between the Early Upper Paleolithic and the Mesolithic is qualitatively predicted by genetics. Similarly, both skeletal and genetic height remained constant between the Mesolithic and Neolithic and increased between the Neolithic and Bronze Age. Sitting height changes much less than standing height-consistent with genetic predictions-although genetics predicts a small post-Neolithic increase that is not observed in skeletal remains. Geographic variation in stature is also qualitatively consistent with genetic predictions, particularly with respect to latitude. Finally, we hypothesize that an observed decrease in genetic heel bone mineral density in the Neolithic reflects adaptation to the decreased mobility indicated by decreased femoral bending strength. This study provides a model for interpreting phenotypic changes predicted from ancient DNA and demonstrates how they can be combined with phenotypic measurements to understand the relative contribution of genetic and developmentally plastic responses to environmental change., Competing Interests: The authors declare no competing interest., (Copyright © 2019 the Author(s). Published by PNAS.)

Ecosystem-bedrock interactions power the biogeochemical cycles of Earth's shallow crust, supporting life, stimulating substrate transformation, and spurring evolutionary innovation. While oxidative processes have dominated half of terrestrial history, the relative contribution of the biosphere and its chemical fingerprints on Earth's developing regolith are still poorly constrained. Here, we report results from a two-year incipient weathering experiment. We found that the mass release and compartmentalization of major elements during weathering of granite, rhyolite, schist and basalt was rock-specific and regulated by ecosystem components. A tight interplay between physiological needs of different biota, mineral dissolution rates, and substrate nutrient availability resulted in intricate elemental distribution patterns. Biota accelerated CO 2 mineralization over abiotic controls as ecosystem complexity increased, and significantly modified the stoichiometry of mobilized elements. Microbial and fungal components inhibited element leaching (23.4% and 7%), while plants increased leaching and biomass retention by 63.4%. All biota left comparable biosignatures in the dissolved weathering products. Nevertheless, the magnitude and allocation of weathered fractions under abiotic and biotic treatments provide quantitative evidence for the role of major biosphere components in the evolution of upper continental crust, presenting critical information for large-scale biogeochemical models and for the search for stable in situ biosignatures beyond Earth.

Challenges to the reclamation of pyritic mine tailings arise from in situ acid generation that severely constrains the growth of natural revegetation. While acid mine drainage (AMD) microbial communities are well-studied under highly acidic conditions, fewer studies document the dynamics of microbial communities that generate acid from pyritic material under less acidic conditions that can allow establishment and support of plant growth. This research characterizes the taxonomic composition dynamics of microbial communities present during a 6-year compost-assisted phytostabilization field study in extremely acidic pyritic mine tailings. A complementary microcosm experiment was performed to identify successional community populations that enable the acidification process across a pH gradient. Taxonomic profiles of the microbial populations in both the field study and microcosms reveal shifts in microbial communities that play pivotal roles in facilitating acidification during the transition between moderately and highly acidic conditions. The potential co-occurrence of organoheterotrophic and lithoautotrophic energy metabolisms during acid generation suggests the importance of both groups in facilitating acidification. Taken together, this research suggests that key microbial populations associated with pH transitions could be used as bioindicators for either sustained future plant growth or for acid generation conditions that inhibit further plant growth.

Phytostabilized highly acidic, pyritic mine tailings are susceptible to re-acidification over time despite initial addition of neutralizing amendments. Studies examining plant-associated microbial dynamics during re-acidification of phytostabilized regions are sparse. To address this, we characterized the rhizosphere and bulk bacterial communities of buffalo grass used in the phytostabilization of metalliferous, pyritic mine tailings undergoing re-acidification at the Iron King Mine and Humboldt Smelter Superfund Site in Dewey-Humboldt, AZ. Plant-associated substrates representing a broad pH range (2.35-7.76) were sampled to (1) compare the microbial diversity and community composition of rhizosphere and bulk compartments across a pH gradient, and (2) characterize how re-acidification affects the abundance and activity of the most abundant plant growth-promoting bacteria (PGPB; including N 2 -fixing) versus acid-generating bacteria (AGB; including Fe-cycling/S-oxidizing). Results indicated that a shift in microbial diversity and community composition occurred at around pH 4. At higher pH (>4) the species richness and community composition of the rhizosphere and bulk compartments were similar, and PGPB, such as Pseudomonas , Arthrobacter , Devosia , Phyllobacterium , Sinorhizobium , and Hyphomicrobium , were present and active in both compartments with minimal presence of AGB. In comparison, at lower pH (<4) the rhizosphere had a significantly higher number of species than the bulk ( p < 0.05) and the compartments had significantly different community composition (unweighted UniFrac; PERMANOVA, p < 0.05). Whereas some PGPB persisted in the rhizosphere at lower pH, including Arthrobacter and Devosia , they were absent from the bulk. Meanwhile, AGB dominated in both compartments; the most abundant were the Fe-oxidizer Leptospirillum and Fe-reducers Acidibacter and Acidiphilium , and the most active was the Fe-reducer Aciditerrimonas . This predominance of AGB at lower pH, and even their minimal presence at higher pH, contributes to acidifying conditions and poses a significant threat to sustainable plant establishment. These findings have implications for phytostabilization field site management and suggest re-application of compost or an alternate buffering material may be required in regions susceptible to re-acidification to maintain a beneficial bacterial community conducive to long-term plant establishment.

Genetic predictions of height differ among human populations and these differences have been interpreted as evidence of polygenic adaptation. These differences were first detected using SNPs genome-wide significantly associated with height, and shown to grow stronger when large numbers of sub-significant SNPs were included, leading to excitement about the prospect of analyzing large fractions of the genome to detect polygenic adaptation for multiple traits. Previous studies of height have been based on SNP effect size measurements in the GIANT Consortium meta-analysis. Here we repeat the analyses in the UK Biobank, a much more homogeneously designed study. We show that polygenic adaptation signals based on large numbers of SNPs below genome-wide significance are extremely sensitive to biases due to uncorrected population stratification. More generally, our results imply that typical constructions of polygenic scores are sensitive to population stratification and that population-level differences should be interpreted with caution., Editorial Note: This article has been through an editorial process in which the authors decide how to respond to the issues raised during peer review. The Reviewing Editor's assessment is that all the issues have been addressed (see decision letter)., Competing Interests: MS, RM, AG, AB, AM, MT, CC, JH, MD, NP, IM, DR, SS No competing interests declared, BN Ben Neale is a member and on the scientific advisory board of Deep Genomics, a consultant for Camp4 Therapeutics Corporation, a consultant for Merck & Co., a consultant for Takeda Phamaceutical, and a consultant for Avanir Pharmaceuticals. None of these entities played a role in determining the content of this paper., (© 2019, Sohail et al.)

This study shows thallium (Tl) concentrations in Brassica juncea (Indian mustard) tissue are more than an order of magnitude higher (3830 μg/kg) than that of the substrate (100 μg/kg) and are strongly influenced by the underlying mineralogy; i.e., Tl bioaccessibility depends on the mineral structure: K-feldspar > Mn nodule > hendricksite mica. The majority of Tl for all substrates is contained in edible parts of the plant, i.e., leaves (41% of total Tl, on average) ≥ flower stems (34%) > seed pods (11%) ≈ stems (10%) > flowers (3%). We also show that Tl isotope fractionation induced by B. juncea is substantial, at nearly 10 ε 205 Tl units, and generates systematic plant-specific patterns. Progressive plant growth strongly fractionates Tl isotopes, discriminating against 205 Tl as the plant matures. Thus, 205 Tl values are systematically higher in the early formed stem (ε 205 Tl avg = +2.5) than in plant elements formed later (ε 205 Tl avg = -2.5 to +0.1), which demonstrates the large degree of translocation and the associated effects during plant growth. This study establishes the potential of Tl isotopes as a new tool for understanding heavy metal (re)distribution during anthropogenic and geologic processes and the utility of such information in environmental and health-related planning and in phytomining or bioprospecting.

Synthetic monorhamnolipids differ from biologically produced material because they are produced as single congeners, depending on the β-hydroxyalkanoic acid used during synthesis. Each congener is produced as one of four possible diastereomers resulting from two chiral centers at the carbinols of the lipid tails [(R,R), (R,S), (S,R) and (S,S)]. We compare the biodegradability (CO 2 respirometry), acute toxicity (Microtox assay), embryo toxicity (Zebrafish assay), and cytotoxicity (xCELLigence and MTS assays) of synthetic rhamnosyl-β-hydroxydecanoyl-β-hydroxydecanoate (Rha-C10-C10) monorhamnolipids against biosynthesized monorhamnolipid mixtures (bio-mRL). All Rha-C10-C10 diastereomers and bio-mRL were inherently biodegradable ranging from 34 to 92% mineralized. The Microtox assay showed all Rha-C10-C10 diastereomers and bio-mRL are slightly toxic according to the US EPA ecotoxicity categories with 5 min EC 50 values ranging from 39.6 to 87.5 μM. The zebrafish assay showed that of 22 developmental endpoints tested, only mortality was observed at 120 h post fertilization; all Rha-C10-C10 diastereomers and bio-mRL caused significant mortality at 640 μM, except the Rha-C10-C10 (R,R) which showed no developmental effects. xCELLigence and MTS showed IC 50 values ranging from 103.4 to 191.1 μM for human lung cell line H1299 after 72 h exposure. These data provide key information regarding Rha-C10-C10 diastereomers that is pertinent when considering potential applications., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Environmental and health risk concerns relating to airborne particles from mining operations have focused primarily on smelting activities. However, there are only three active copper smelters and less than a dozen smelters for other metals compared to an estimated 500000 abandoned and unreclaimed hard rock mine tailings in the US that have the potential to generate dust. The problem can also extend to modern tailings impoundments, which may take decades to build and remain barren for the duration before subsequent reclamation. We examined the impact of vegetation cover and irrigation on dust emissions and metal(loid) transport from mine tailings during a phytoremediation field trial at the Iron King Mine and Humboldt Smelter Superfund (IKMHSS) site. Measurements of horizontal dust flux following phytoremediation reveals that vegetated plots with 16% and 32% canopy cover enabled an average dust deposition of 371.7 and 606.1 g m -2 y -1 , respectively, in comparison to the control treatment which emitted dust at an average rate of 2323 g m -2 y -1 . Horizontal dust flux and dust emissions from the vegetated field plots are comparable to emission rates in undisturbed grasslands. Further, phytoremediation was effective at reducing the concentration of fine particulates, including PM 1 , PM 2.5 , and PM 4 , which represent the airborne particulates with the greatest health risks and the greatest potential for long-distance transport. This study demonstrates that phytoremediation can substantially decrease dust emissions as well as the transport of windblown contaminants from mine tailings.

The availability of genome-wide genetic data on hundreds of thousands of people has led to an equally rapid growth in methodologies available to analyse these data. While the motivation for undertaking genome-wide association studies (GWAS) is identification of genetic markers associated with complex traits, once generated these data can be used for many other analyses. GWAS have demonstrated that complex traits exhibit a highly polygenic genetic architecture, often with shared genetic risk factors across traits. New methods to analyse data from GWAS are increasingly being used to address a diverse set of questions about the aetiology of complex traits and diseases, including psychiatric disorders. Here, we give an overview of some of these methods and present examples of how they have contributed to our understanding of psychiatric disorders. We consider: (i) estimation of the extent of genetic influence on traits, (ii) uncovering of shared genetic control between traits, (iii) predictions of genetic risk for individuals, (iv) uncovering of causal relationships between traits, (v) identifying causal single-nucleotide polymorphisms and genes or (vi) the detection of genetic heterogeneity. This classification helps organise the large number of recently developed methods, although some could be placed in more than one category. While some methods require GWAS data on individual people, others simply use GWAS summary statistics data, allowing novel well-powered analyses to be conducted at a low computational burden.

Major depressive disorder (MDD) is a common illness accompanied by considerable morbidity, mortality, costs, and heightened risk of suicide. We conducted a genome-wide association meta-analysis based in 135,458 cases and 344,901 controls and identified 44 independent and significant loci. The genetic findings were associated with clinical features of major depression and implicated brain regions exhibiting anatomical differences in cases. Targets of antidepressant medications and genes involved in gene splicing were enriched for smaller association signal. We found important relationships of genetic risk for major depression with educational attainment, body mass, and schizophrenia: lower educational attainment and higher body mass were putatively causal, whereas major depression and schizophrenia reflected a partly shared biological etiology. All humans carry lesser or greater numbers of genetic risk factors for major depression. These findings help refine the basis of major depression and imply that a continuous measure of risk underlies the clinical phenotype.

Direct revegetation, or phytostabilization, is a containment strategy for contaminant metals associated with mine tailings in semiarid regions. The weathering of sulfide ore-derived tailings frequently drives acidification that inhibits plant establishment resulting in materials prone to wind and water dispersal. The specific objective of this study was to associate pyritic mine waste acidification, characterized through pore-water chemistry analysis, with dynamic changes in microbial community diversity and phylogenetic composition, and to evaluate the influence of different treatment strategies on the control of acidification dynamics. Samples were collected from a highly instrumented one-year mesocosm study that included the following treatments: 1) unamended tailings control; 2) tailings amended with 15% compost; and 3) the 15% compost-amended tailings planted with Atriplex lentiformis. Tailings samples were collected at 0, 3, 6 and 12months and pore water chemistry was monitored as an indicator of acidification and weathering processes. Results confirmed that the acidification process for pyritic mine tailings is associated with a temporal progression of bacterial and archaeal phylotypes from pH sensitive Thiobacillus and Thiomonas to communities dominated by Leptospirillum and Ferroplasma. Pore-water chemistry indicated that weathering rates were highest when Leptospirillum was most abundant. The planted treatment was most successful in disrupting the successional evolution of the Fe/S-oxidizing community. Plant establishment stimulated growth of plant-growth-promoting heterotrophic phylotypes and controlled the proliferation of lithoautotrophic Fe/S-oxidizers. The results suggest the potential for eco-engineering a microbial inoculum to stimulate plant establishment and inhibit proliferation of the most efficient Fe/S-oxidizing phylotypes., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Genomic prediction has the potential to contribute to precision medicine. However, to date, the utility of such predictors is limited due to low accuracy for most traits. Here theory and simulation study are used to demonstrate that widespread pleiotropy among phenotypes can be utilised to improve genomic risk prediction. We show how a genetic predictor can be created as a weighted index that combines published genome-wide association study (GWAS) summary statistics across many different traits. We apply this framework to predict risk of schizophrenia and bipolar disorder in the Psychiatric Genomics consortium data, finding substantial heterogeneity in prediction accuracy increases across cohorts. For six additional phenotypes in the UK Biobank data, we find increases in prediction accuracy ranging from 0.7% for height to 47% for type 2 diabetes, when using a multi-trait predictor that combines published summary statistics from multiple traits, as compared to a predictor based only on one trait.

Phytostabilization is a cost-effective long-term bioremediation technique for the immobilization of metalliferous mine tailings. However, the biogeochemical processes affecting metal(loid) molecular stabilization and mobility in the root zone remain poorly resolved. The roots of Prosopis juliflora grown for up to 36 months in compost-amended pyritic mine tailings from a federal Superfund site were investigated by microscale and bulk synchrotron X-ray absorption spectroscopy (XAS) and multiple energy micro-X-ray fluorescence imaging to determine iron, arsenic, and sulfur speciation, abundance, and spatial distribution. Whereas ferrihydrite-bound As(V) species predominated in the initial bulk mine tailings, the rhizosphere speciation of arsenic was distinctly different. Root-associated As(V) was immobilized on the root epidermis bound to ferric sulfate precipitates and within root vacuoles as trivalent As(III)-(SR) 3  tris-thiolate complexes. Molar Fe-to-As ratios of root epidermis tissue were two times higher than the 15% compost-amended bulk tailings growth medium. Rhizoplane-associated ferric sulfate phases that showed a high capacity to scavenge As(V) were dissimilar from the bulk-tailings mineralogy as shown by XAS and X-ray diffraction, indicating a root-surface mechanism for their formation or accumulation.

Plant establishment during phytostabilization of legacy mine tailings in semiarid regions is challenging due to low pH, low organic carbon, low nutrients, and high toxic metal(loid) concentrations. Plant-associated bacterial communities are particularly important under these harsh conditions because of their beneficial services to plants. We hypothesize that bacterial colonization profiles on rhizoplane surfaces reflect deterministic processes that are governed by plant health and the root environment. The aim of this study was to identify associations between bacterial colonization patterns on buffalo grass (Buchloe dactyloides) rhizoplanes and both plant status (leaf chlorophyll and plant cover) and substrate biogeochemistry (pH, electrical conductivity, total organic carbon, total nitrogen, and rhizosphere microbial community). Buffalo grass plants from mesocosm- and field-scale phytostabilization trials conducted with tailings from the Iron King Mine and Humboldt Smelter Superfund Site in Dewey-Humboldt, Arizona, were analyzed. These tailings are extremely acidic and have arsenic and lead concentrations of 2-4 g kg -1 substrate. Bacterial communities on rhizoplanes and in rhizosphere-associated substrate were characterized using fluorescence in situ hybridization and 16S rRNA gene amplicon sequencing, respectively. The results indicated that the metabolic status of rhizoplane bacterial colonizers is significantly related to plant health. Principal component analysis revealed that root-surface Alphaproteobacteria relative abundance was associated most strongly with substrate pH and Gammaproteobacteria relative abundance associated strongly with substrate pH and plant cover. These factors also affected the phylogenetic profiles of the associated rhizosphere communities. In summary, rhizoplane bacterial colonization patterns are plant specific and influenced by plant status and rhizosphere biogeochemical conditions.

Rare earth elements (REE) are vital for modern technologies and considered critical materials. This study investigated monorhamnolipid biosurfactant interactions with REE as the basis for REE recovery technology. Conditional stability constants (log β), measured using a resin-based ion exchange method, are reported for 16 REE and metals. These results were combined with existing data for 10 other metals to assess comparative strength and determinants of binding. The stability constants could be divided into three groups: weakly, moderately, and strongly bound. The REE were all in the strongly bound group (UO 2 2+ , Eu 3+ , Nd 3+ , Tb 3+ , Dy 3+ , La 3+ , Cu 2+ , Al 3+ , Pb 2+ , Y 3+ , Pr 3+ , and Lu 3+ ) with log β ranging from 9.82 to 8.20. The elements Cd 2+ , In 3+ , Zn 2+ , Fe 3+ , Hg 2+ , and Ca 2+ were moderately bound with log β=7.17-4.10. Finally, Sr 2+ , Co 2+ , Ni 2+ , UO 2 2+ , Ba 2+ , Mn 2+ , Mg 2+ , Rb + , and K + were weakly bound with log β=3.95-0.96. Two log β values are reported for the uranyl ion due to two distinct binding regions. A mixed metals study and associated selectivity coefficients confirmed monorhamnolipids preferentially remove metals with large log β values over those with smaller values. Preferential complexation by monorhamnolipids may constitute a green pathway for recovery of REE from alternative, non-traditional sources., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Community health workers (promotores de salud) have the ability to empower communities to mitigate negative health outcomes. Current training efforts in environmental topics are lacking. This project addressed this gap by developing 4 transferable training modules on environmental health. By applying a series of surveys, interviews, and trainings, we evaluated their relevance. Partners provided favorable feedback for 3 of the 4 modules. It was also learned that the development method could be improved by engaging technically trained promotores de salud in the role of co-creators. This project has implications for environmental justice communities as it can lessen information disparities.

When asked to translate utterances, people might merely make sure that their translations have the same meaning as the source, but they might also maintain aspects of sentence form across languages. We report two experiments in which English-German and German-English bilinguals (without specialist translator training) repeated German ditransitive sentences whose meaning was compatible with more than one grammatical form or translated them into English. Participants almost invariably repeated the sentences accurately, thereby retaining the grammatical structure. Importantly, Experiment 1 found that they tended to repeat grammatical form across languages. Experiment 2 included a condition with sentences that had no grammatical equivalent form in English; here participants tended to persist in the order of thematic roles. We argue that cross-linguistic structural priming plays a major role in the act of translation.

The evolution of solution aggregates of the anionic form of the native monorhamnolipid (mRL) mixture produced by Pseudomonas aeruginosa ATCC 9027 is explored at pH 8.0 using both experimental and computational approaches. Experiments utilizing surface tension measurements, dynamic light scattering, and both steady-state and time-resolved fluorescence spectroscopy reveal solution aggregation properties. All-atom molecular dynamics simulations on self-assemblies of the most abundant monorhamnolipid molecule, l-rhamnosyl-β-hydroxydecanoyl-β-hydroxydecanoate (Rha-C10-C10), in its anionic state explore the formation of aggregates and the role of hydrogen bonding, substantiating the experimental results. At pH 8.0, at concentrations above the critical aggregation concentration of 201 μM but below ∼7.5 mM, small premicelles exist in solution; above ∼7.5 mM, micelles with hydrodynamic radii of ∼2.5 nm dominate, although two discrete populations of larger lamellar aggregates (hydrodynamic radii of ∼10 and 90 nm) are also present in solution in much smaller number densities. The critical aggregation number for the micelles is determined to be ∼26 monomers/micelle using fluorescence quenching measurements, with micelles gradually increasing in size with monorhamnolipid concentration. Molecular dynamics simulations on systems with between 10 and 100 molecules of Rha-C10-C10 indicate the presence of stable premicelles of seven monomers with the most prevalent micelle being ∼25 monomers and relatively spherical. A range of slightly larger micelles of comparable stability can also exist that become increasing elliptical with increasing monomer number. Intermolecular hydrogen bonding is shown to play a significant role in stabilization of these aggregates. In total, the computational results are in excellent agreement with the experimental results.

Global deserts occupy one-third of the Earth's surface and contribute significantly to organic carbon storage, a process at risk in dryland ecosystems that are highly vulnerable to climate-driven ecosystem degradation. The forces controlling desert ecosystem degradation rates are poorly understood, particularly with respect to the relevance of the arid-soil microbiome. Here we document correlations between increasing aridity and soil bacterial and archaeal microbiome composition along arid to hyperarid transects traversing the Atacama Desert, Chile. A meta-analysis reveals that Atacama soil microbiomes exhibit a gradient in composition, are distinct from a broad cross-section of nondesert soils, and yet are similar to three deserts from different continents. Community richness and diversity were significantly positively correlated with soil relative humidity (SoilRH). Phylogenetic composition was strongly correlated with SoilRH, temperature, and electrical conductivity. The strongest and most significant correlations between SoilRH and phylum relative abundance were observed for Acidobacteria , Proteobacteria , Planctomycetes , Verrucomicrobia , and Euryarchaeota (Spearman's rank correlation [ r s ] = >0.81; false-discovery rate [ q ] = ≤0.005), characterized by 10- to 300-fold decreases in the relative abundance of each taxon. In addition, network analysis revealed a deterioration in the density of significant associations between taxa along the arid to hyperarid gradient, a pattern that may compromise the resilience of hyperarid communities because they lack properties associated with communities that are more integrated. In summary, results suggest that arid-soil microbiome stability is sensitive to aridity as demonstrated by decreased community connectivity associated with the transition from the arid class to the hyperarid class and the significant correlations observed between soilRH and both diversity and the relative abundances of key microbial phyla typically dominant in global soils. IMPORTANCE We identify key environmental and geochemical factors that shape the arid soil microbiome along aridity and vegetation gradients spanning over 300 km of the Atacama Desert, Chile. Decreasing average soil relative humidity and increasing temperature explain significant reductions in the diversity and connectivity of these desert soil microbial communities and lead to significant reductions in the abundance of key taxa typically associated with fertile soils. This finding is important because it suggests that predicted climate change-driven increases in aridity may compromise the capacity of the arid-soil microbiome to sustain necessary nutrient cycling and carbon sequestration functions as well as vegetative cover in desert ecosystems, which comprise one-third of the terrestrial biomes on Earth.

Phytostabilization is a remediation technology that uses plants for in-situ stabilization of contamination in soils and mine tailings. The objective of this study was to identify native plant species with potential for phytostabilization of the abandoned mine tailings in Nacozari, Sonora in northern Mexico. A flora of 42 species in 16 families of angiosperms was recorded on the tailings site and the abundance of the most common perennial species was estimated. Four of the five abundant perennial species showed evidence of regeneration: the ability to reproduce and establish new seedlings. A comparison of selected physicochemical properties of the tailings in vegetated patches with adjacent barren areas suggests that pH, electrical conductivity, texture, and concentration of potentially toxic elements do not limit plant distribution. For the most abundant species, the accumulation factor for most metals was <1, with the exception of Zn in two species. A short-term experiment on adaptation revealed limited evidence for the formation of local ecotypes in Prosopis velutina and Amaranthus watsonii . Overall, the results of this study indicate that five native plant species might have potential for phytostabilization of the Nacozari tailings and that seed could be collected locally to revegetate the site. More broadly, this study provides a methodology that can be used to identify native plants and evaluate their phytostabilization potential for similar mine tailings., Competing Interests: The authors declare there are no competing interests.

Rhamnolipids are amphiphilic glycolipids biosynthesized by bacteria that, due to their low toxicity and biodegradability, are potential replacements for synthetic surfactants. The previously limited access to pure materials at the gram scale has hindered extensive characterization of rhamnolipid structure-performance behavior. Here, we present an efficient and versatile synthetic methodology from which four diastereomers of the most common monorhamnolipid, α-rhamnopyranosyl-β-hydroxydecanoyl-β-hydroxydecanoate, are prepared and subsequently characterized. Exploration of their behavior at the air-water interface is reported and analyzed in terms of the absolute configuration of the lipid tail carbinols at pH 4.0 and 8.0. All diastereomers exhibit a minimum surface tension of about 28 mN/m without a significant difference between the protonated (nonionic) or deprotonated (anionic) states. At pH 4.0 (nonionic), all diastereomers have a critical micelle concentration (CMC) in the micromolar range. At pH 8.0 (anionic), CMC values for the (R,R), (S,S), and (S,R) diastereomers are approximately an order of magnitude higher than in their nonionic states, whereas the (R,S) diastereomer exhibits a CMC about five times larger.

Background: Patients with asthma and healthy controls differ in bacterial colonization of the respiratory tract. The upper airways have been shown to reflect colonization of the lower airways, the actual site of inflammation in asthma, which is hardly accessible in population studies., Objective: We sought to characterize the bacterial communities at 2 sites of the upper respiratory tract obtained from children from a rural area and to relate these to asthma., Methods: The microbiota of 327 throat and 68 nasal samples from school-age farm and nonfarm children were analyzed by 454-pyrosequencing of the bacterial 16S ribosomal RNA gene., Results: Alterations in nasal microbiota but not of throat microbiota were associated with asthma. Children with asthma had lower α- and β-diversity of the nasal microbiota as compared with healthy control children. Furthermore, asthma presence was positively associated with a specific operational taxonomic unit from the genus Moraxella in children not exposed to farming, whereas in farm children Moraxella colonization was unrelated to asthma. In nonfarm children, Moraxella colonization explained the association between bacterial diversity and asthma to a large extent., Conclusions: Asthma was mainly associated with an altered nasal microbiota characterized by lower diversity and Moraxella abundance. Children living on farms might not be susceptible to the disadvantageous effect of Moraxella. Prospective studies may clarify whether Moraxella outgrowth is a cause or a consequence of loss in diversity., (Copyright © 2016 American Academy of Allergy, Asthma & Immunology. All rights reserved.)