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  1. Lipids represent a dynamic, yet stable pool of microbially-derived soil carbon

    Rempfert, Kaitlin R. ; Bell, Sheryl L. ; Kasanke, Christopher P. ; ... - Soil Biology and Biochemistry
    There is an emerging consensus that microorganisms are a primary source of persistent, slow-cycling soil organic matter (SOM), however which microbial residues contribute to SOM and what controls their accumulation remains unresolved. Lipids are a commonly overlooked biomolecular pool that could contribute significantly to stable SOM. While current estimates for phospholipid degradation in soils are rapid, lipids are structurally heterogeneous molecules that could turnover at different rates. Through a year-long soil incubation and compound-specific, stable isotope probing (SIP)-lipidomics, we were able to rigorously track the persistence of lipid compounds in silty and sandy switchgrass bioenergy crop soils. Here, we assessedmore » the influence of lipid structure on soil lipid accrual and degradation as moderated by soil texture, since mineral association is presumed to be the primary mechanism for lipid persistence. After rapid incorporation of 13C glucose into microbial biomass, we found 13C label was retained broadly across chemically diverse lipid classes, even after one year. 13C-labeled lipid profiles varied significantly with soil texture; however, we found no difference between sandy and silty soils in lipid retention, suggesting soil texture may only play a minor role in modulating lipid persistence. Only two lipid subclasses were found to be persistent (i.e., retention of 13C label without significant degradation or production): phosphatidylinositol lipids and hydroxyceramide lipids, both of which are negatively charged, possibly facilitating stabilization by mineral complexation. However, several other subclasses displayed substantial ongoing production. In particular, the accumulation of triacylglycerol lipids across soil textures suggests that storage lipids may be an important component of SOC, highlighting a potential target for management strategies to promote C retention by lipid accrual. Overall, the retention for over a year of 13C label in microbial intact lipid biomarkers reveals the importance of efficient biomass production and turnover when considering microbial C contributions to SOM.« less

  2. Experimental Validation of a Module Cell Cracking Model

    Bosco, Nick - IEEE Journal of Photovoltaics
    The What's Cracking app can predict how changes in crystalline silicon photovoltaic (PV) module materials, design, and mounting affect its susceptibility for cell fracture under uniform loading. This work has experimentally validated the app. A set of commercial crystalline silicon PV modules was obtained for this study. The modules were uniformly loaded at three different mounting points, and their subsequent cell fractures were recorded. A large sample size allowed for the development of an experimental statistical model for cell fracture. Here, the comparison of the experiment to predictions from the app is in excellent agreement. Both experimental and modeling resultsmore » also elucidate how moving the module mounting points toward the center of the module increases the probability of cell fracture.« less

  3. Getting Ahead of the Curve: Assessment of New Photovoltaic Module Reliability Risks Associated With Projected Technological Changes

    Zuboy, Jarett ; Springer, Martin ; Palmiotti, Elizabeth C. ; ... - IEEE Journal of Photovoltaics

  4. Genomic Features Predict Bacterial Life History Strategies in Soil, as Identified by Metagenomic Stable Isotope Probing

    Barnett, Samuel E. ; Egan, Rob ; Foster, Brian ; ... - mBio (Online)
    Soil microbes are major players in the global carbon cycle, yet we still have little understanding of how the carbon cycle operates in soil communities. A major limitation is that carbon metabolism lacks discrete functional genes that define carbon transformations.

  5. Plasmonic nanorod probes’ journey inside plant cells for in vivo SERS sensing and multimodal imaging

    Cupil-Garcia, Vanessa ; Li, Joy Q. ; Norton, Stephen J. ; ... - Nanoscale
    Nanoparticle-based platforms are gaining strong interest in plant biology and bioenergy research to monitor and control biological processes in whole plants. However, in vivo monitoring of biomolecules using nanoparticles inside plant cells remains challenging due to the impenetrability of the plant cell wall to nanoparticles beyond the exclusion limits (5–20 nm). To overcome this physical barrier, we have designed unique bimetallic silver-coated gold nanorods (AuNR@Ag) capable of entering plant cells, while conserving key plasmonic properties in the near-infrared (NIR). To demonstrate cellular internalization and tracking of the nanorods inside plant tissue, we used a comprehensive multimodal imaging approach that includedmore » transmission electron microscopy (TEM), confocal fluorescence microscopy, two-photon luminescence (TPL), X-ray fluorescence microscopy (XRF), and photoacoustics imaging (PAI). We successfully acquired SERS signals of nanorods in vivo inside plant cells of tobacco leaves. On the same leaf samples, we applied orthogonal imaging methods, TPL and PAI techniques for in vivo imaging of the nanorods. Here this study first demonstrates the intracellular internalization of AuNR@Ag inside whole plant systems for in vivo SERS analysis in tobacco cells. This work demonstrates the potential of this nanoplatform as a new nanotool for intracellular in vivo biosensing for plant biology.« less

  6. The Transcriptional Response of Soil Bacteria to Long-Term Warming and Short-Term Seasonal Fluctuations in a Terrestrial Forest

    Roy Chowdhury, Priyanka ; Golas, Stefan M. ; Alteio, Lauren V. ; ... - Frontiers in Microbiology
    Terrestrial ecosystems are an important carbon store, and this carbon is vulnerable to microbial degradation with climate warming. After 30 years of experimental warming, carbon stocks in a temperate mixed deciduous forest were observed to be reduced by 30% in the heated plots relative to the controls. In addition, soil respiration was seasonal, as was the warming treatment effect. We therefore hypothesized that long-term warming will have higher expressions of genes related to carbohydrate and lipid metabolism due to increased utilization of recalcitrant carbon pools compared to controls. Because of the seasonal effect of soil respiration and the warming treatment,more » we further hypothesized that these patterns will be seasonal. We used RNA sequencing to show how the microbial community responds to long-term warming (~30 years) in Harvard Forest, MA. Total RNA was extracted from mineral and organic soil types from two treatment plots (+5°C heated and ambient control), at two time points (June and October) and sequenced using Illumina NextSeq technology. Treatment had a larger effect size on KEGG annotated transcripts than on CAZymes, while soil types more strongly affected CAZymes than KEGG annotated transcripts, though effect sizes overall were small. Although, warming showed a small effect on overall CAZymes expression, several carbohydrate-associated enzymes showed increased expression in heated soils (~68% of all differentially expressed transcripts). Further, exploratory analysis using an unconstrained method showed increased abundances of enzymes related to polysaccharide and lipid metabolism and decomposition in heated soils. Compared to long-term warming, we detected a relatively small effect of seasonal variation on community gene expression. Together, these results indicate that the higher carbohydrate degrading potential of bacteria in heated plots can possibly accelerate a self-reinforcing carbon cycle-temperature feedback in a warming climate.« less

  7. An automated multiplexed turbidometric and data collection system for measuring growth kinetics of anaerobes dependent on gaseous substrates

    Hunt, Kristopher A. ; Forbes, Jonathan ; Taub, Fred ; ... - Journal of Microbiological Methods
    Standard methods of monitoring the growth kinetics of anaerobic microorganisms are generally impractical when there is a protracted or indeterminate period of active growth, and when high numbers of samples or replications are required. As part of our studies of the adaptive evolution of a simple anaerobic syntrophic mutualism, requiring the characterization of many isolates and alternative syntrophic pairings, here we developed a multiplexed growth monitoring system using a combination of commercially available electronics and custom designed circuitry and materials. This system automatically monitors up to 64 sealed, and as needed pressurized, culture tubes and reports the growth data inmore » real-time through integration with a customized relational database. The utility of this system was demonstrated by resolving minor differences in growth kinetics associated with the adaptive evolution of a simple microbial community comprised of a sulfate reducing bacterium, Desulfovibrio vulgaris, grown in syntrophic association with Methanococcus maripaludis, a hydrogenotrophic methanogen.« less

  8. Representing the function and sensitivity of coastal interfaces in Earth system models

    Ward, Nicholas D. ; Megonigal, J. Patrick ; Bond-Lamberty, Ben ; ... - Nature Communications

  9. Editorial: The Role of Priming in Terrestrial and Aquatic Ecosystems

    Bianchi, Thomas S. ; Ward, Nicholas D. - Frontiers in Earth Science
    Carbon-containing organic matter (OM) is constantly synthesized from atmospheric carbon dioxide (CO2) by primary producing flora in Earth’s biosphere. The fate of this OM—i.e., how long it persists in the environment before being recycled back to atmospheric CO2 by heterotrophic microbes and fauna—is highly variable, and largely dependent on the diversity of environmental conditions it is exposed to both at its origin and during transport to distant locations. This dynamic cycling of carbon, energy, and matter between the atmosphere and biosphere occurs within and across all types of terrestrial, aquatic, and marine ecosystems. While the underlying biological functions and chemicalmore » reactions related to carbon fixation and decomposition are generally common across ecosystems, the disciplines of terrestrial and aquatic biogeochemistry have historically pursued this topic along separate paths with differing strengths and weaknesses. Although this continues today, several focus areas have recently brought more cross-fertilization between these disciplines. One such focus area where terrestrial and aquatic communities have begun converging is the study of interactive effects on OM decomposition that occur when OM of different origins and reactivities mix. This line of research has embraced the necessity to consider reactivity within the context of the past history and present state of OM in all of its highly diverse forms. Interactive effects on OM cycling were first explored about 100 years ago in the context of soil humus mineralization and have since been termed priming effects. Priming can be defined as the enhancement of recalcitrant (stable) OM breakdown via microbial decay with the addition of a more labile (less-stable) OM source. Priming can involve dissolved and/or particulate OM, in some cases accompanied by nutrients, and results in more efficient decay/consumption of stable OM material than would have occurred otherwise in the absence of the less-stable OM. While much of the work on this topic began in terrestrial systems, aquatic researchers have followed suit and gained momentum in the last decade. Observations of priming in aquatic environments are becoming more widespread, but little consensus has been reached on their role, perhaps because we lack the mechanistic understanding to accurately predict when and where priming effects should occur. The motivation for the collection of studies summarized below is to progress towards a common language, set of experimental approaches, and perspective on the role of priming effects in both terrestrial and aquatic ecosystems.« less

  10. Enhanced aquatic respiration associated with mixing of clearwater tributary and turbid Amazon River waters

    Ward, Nicholas D. ; Sawakuchi, Henrique O. ; Richey, Jeffrey E. ; ... - Frontiers in Earth Science
    When water bodies with unique biogeochemical constituents mix together there is potential for diverse responses by aquatic microbial communities and associated ecosystem functions. Here we evaluate bulk respiration rates under varying mixtures of turbid Amazon River water and two lowland tributaries—the Tapajós and Xingu rivers—based on O2 drawdown in dark rotating incubation chambers. Preliminary experiments containing 50% Tapajós River and 50% Amazon River water were performed during falling water. More detailed experiments containing 5%, 17%, 33%, and 50% tributary water were performed for both the Tapajós and Xingu rivers at 3 different rotation velocities (0, 0.22, and 0.66 m s-1)more » during the falling water period. Respiration rates were higher in the mixtures compared to both river endmembers in most experiments. For both the Xingu and Tapajós rivers a 17% mixture yielded maximal respiration rates that were 1.6 to 2.8 times faster than each tributary, respectively. The 50% mixtures, on the other hand, only yielded 1.4 to 1.9 times amplified respiration rates for the Tapajós and Xingu rivers, respectively, and in one case was respiration was 2.8 times lower in the 50% mixture compared to the tributary. We hypothesize that these enhanced respiration rates are driven, in part, by microbial priming effects that have been previously identified on a molecular level for these rivers. The results of this study suggest that there may be a “sweet spot” for priming effects to occur in terms of the relative abundance of “priming” and “primed” substrates.« less
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