An invaluable firsthand account of life during the Civil War, From Manassas to Appomattox, is the memior of Confederate Lieutenant General James Longstreet, the principle subordinate under General ...Robert E. Lee. An introduction and notes by prominent historian James I. Robertson Jr. and a new foreword by Christian Keller offer insight into the impact of Longstreet's career on American history.
Technological advances are enabling the sequencing of environmental DNA and RNA at increasing depth and with decreasing costs. Metagenomic and transcriptomic analysis of soil microbial communities ...and the assembly of 'population genomes' from soil DNA are therefore now feasible. Although the value of such 'omic' approaches is limited by the associated technical and bioinformatic difficulties, even if these obstacles were eliminated and 'perfect' metagenomes and metatranscriptomes were available, important conceptual challenges remain. This Opinion article considers these conceptual challenges in the context of the current use of omics in soil microbiology, but the main arguments presented are also relevant to the application of omics to marine, freshwater, gut or other environments.
Summary
Nitrogen fertilisation of agricultural soil contributes significantly to emissions of the potent greenhouse gas nitrous oxide (N2O), which is generated during denitrification and, in oxic ...soils, mainly by ammonia oxidisers. Although laboratory cultures of ammonia oxidising bacteria (AOB) and archaea (AOA) produce N2O, their relative activities in soil are unknown. This work tested the hypothesis that AOB dominate ammonia oxidation and N2O production under conditions of high inorganic ammonia (NH3) input, but result mainly from the activity of AOA when NH3 is derived from mineralisation. 1‐octyne, a recently discovered inhibitor of AOB, was used to distinguish N2O production resulting from archaeal and bacterial ammonia oxidation in soil microcosms, and specifically inhibited AOB growth, activity and N2O production. In unamended soils, ammonia oxidation and N2O production were lower and resulted mainly from ammonia oxidation by AOA. The AOA N2O yield relative to nitrite produced was half that of AOB, likely due to additional enzymatic mechanisms in the latter, but ammonia oxidation and N2O production were directly linked in all treatments. Relative contributions of AOA and AOB to N2O production, therefore, reflect their respective contributions to ammonia oxidation. These results suggest potential mitigation strategies for N2O emissions from fertilised agricultural soils.
After stimulation, dendritic cells (DCs) mature and migrate to draining lymph nodes to induce immune responses. As such, autologous DCs generated ex vivo have been pulsed with tumour antigens and ...injected back into patients as immunotherapy. While DC vaccines have shown limited promise in the treatment of patients with advanced cancers including glioblastoma, the factors dictating DC vaccine efficacy remain poorly understood. Here we show that pre-conditioning the vaccine site with a potent recall antigen such as tetanus/diphtheria (Td) toxoid can significantly improve the lymph node homing and efficacy of tumour-antigen-specific DCs. To assess the effect of vaccine site pre-conditioning in humans, we randomized patients with glioblastoma to pre-conditioning with either mature DCs or Td unilaterally before bilateral vaccination with DCs pulsed with Cytomegalovirus phosphoprotein 65 (pp65) RNA. We and other laboratories have shown that pp65 is expressed in more than 90% of glioblastoma specimens but not in surrounding normal brain, providing an unparalleled opportunity to subvert this viral protein as a tumour-specific target. Patients given Td had enhanced DC migration bilaterally and significantly improved survival. In mice, Td pre-conditioning also enhanced bilateral DC migration and suppressed tumour growth in a manner dependent on the chemokine CCL3. Our clinical studies and corroborating investigations in mice suggest that pre-conditioning with a potent recall antigen may represent a viable strategy to improve anti-tumour immunotherapy.
Oxidation of ammonia to nitrite by bacteria and archaea is responsible for global emissions of nitrous oxide directly and indirectly through provision of nitrite and, after further oxidation, nitrate ...to denitrifiers. Their contributions to increasing N2O emissions are greatest in terrestrial environments, due to the dramatic and continuing increases in use of ammonia‐based fertilizers, which have been driven by requirement for increased food production, but which also provide a source of energy for ammonia oxidizers (AO), leading to an imbalance in the terrestrial nitrogen cycle. Direct N2O production by AO results from several metabolic processes, sometimes combined with abiotic reactions. Physiological characteristics, including mechanisms for N2O production, vary within and between ammonia‐oxidizing archaea (AOA) and bacteria (AOB) and comammox bacteria and N2O yield of AOB is higher than in the other two groups. There is also strong evidence for niche differentiation between AOA and AOB with respect to environmental conditions in natural and engineered environments. In particular, AOA are favored by low soil pH and AOA and AOB are, respectively, favored by low rates of ammonium supply, equivalent to application of slow‐release fertilizer, or high rates of supply, equivalent to addition of high concentrations of inorganic ammonium or urea. These differences between AOA and AOB provide the potential for better fertilization strategies that could both increase fertilizer use efficiency and reduce N2O emissions from agricultural soils. This article reviews research on the biochemistry, physiology and ecology of AO and discusses the consequences for AO communities subjected to different agricultural practices and the ways in which this knowledge, coupled with improved methods for characterizing communities, might lead to improved fertilizer use efficiency and mitigation of N2O emissions.
A schematic representation of changes in AO communities and directly AO‐associated nitrous oxide emissions during incubation of soil after addition of single application of high inorganic ammonium‐based fertilizer or with slow release of ammonium from soil organic nitrogen or a slow release fertilizer.
Microbial ecology, the scientific study of interactions between natural microbial communities and their environments, has been facilitated by the application of molecular and 'omics'-based techniques ...that overcome some of the limitations of cultivation-based studies. This has increased emphasis on community ecology and 'microbiome' studies, but the majority address technical, rather than scientific challenges. Most are descriptive, do not address scientific aims or questions and are not designed to increase understanding or test hypotheses. The term 'hypothesis' is increasingly misused and critical testing of ideas or theory is restricted to a small minority of studies. This article discusses current microbial ecology research within the context of four approaches: description, induction, inference to the best explanation and deduction. The first three of these do not follow the established scientific method and are not based on scientific ecological questions. Observations are made and sometimes compared with published data, sometimes with attempts to explain findings in the context of existing ideas or hypotheses, but all lack objectivity and are biased by the observations made. By contrast, deductive studies address ecological questions and attempt to explain currently unexplained phenomena through the construction of hypotheses, from mechanism-based assumptions, that generate predictions that are then tested experimentally. Identification of key scientific questions, research driven by meaningful hypotheses and adoption of scientific method are essential for progress in microbial ecology, rather than the current emphasis on descriptive approaches that address only technical challenges. It is, therefore, imperative that we carefully consider and define the fundamental scientific questions that drive our own research and focus on ideas, concepts and hypotheses that can increase understanding, and only then consider which techniques are required for experimental testing. This article is part of the theme issue 'Conceptual challenges in microbial community ecology'.
Classical Pasts Porter, James I
2021, 2005, 2021-02-09
eBook
The term "classical" is used to describe everything from the poems of Homer to entire periods of Greek and Roman antiquity. But just how did the concept evolve? This collection of essays by leading ...classics scholars from the United States and Europe challenges the limits of the current understanding of the term. The book seeks not to arrive at a final definition, but rather to provide a cultural history of the concept by exploring how the meanings of "classical" have been created, recreated, and rejected over time. The book asks questions that have been nearly absent from the scholarly literature. Does "classical" refer to a specific period of history or to the artistic products of that time? How has its definition changed? Did those who lived in classical times have some understanding of what the term "classical" has meant? How coherent, consistent, or even justified is the term? The book's introduction provides a generous theoretical and historical overview. It is followed by eleven chapters in which the contributors argue for the existence not of a single classical past, but of multiple, competing classical pasts. The essays address a broad range of topics--Homer and early Greek poetry and music, Isocrate, Hellenistic and Roman art, Cicero and Greek philosophy, the history of Latin literature, imperial Greek literature, and more. The most up-to-date and challenging treatment of the topic available, this collection will be of lasting interest to students and scholars of ancient and modern literature, art, and cultural history.
Stem cells reside in specialized microenvironments known as niches. During Drosophila development, glial cells provide a niche that sustains the proliferation of neural stem cells (neuroblasts) ...during starvation. We now find that the glial cell niche also preserves neuroblast proliferation under conditions of hypoxia and oxidative stress. Lipid droplets that form in niche glia during oxidative stress limit the levels of reactive oxygen species (ROS) and inhibit the oxidation of polyunsaturated fatty acids (PUFAs). These droplets protect glia and also neuroblasts from peroxidation chain reactions that can damage many types of macromolecules. The underlying antioxidant mechanism involves diverting PUFAs, including diet-derived linoleic acid, away from membranes to the core of lipid droplets, where they are less vulnerable to peroxidation. This study reveals an antioxidant role for lipid droplets that could be relevant in many different biological contexts.
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•Oxidative stress stimulates lipid droplet biosynthesis in a neural stem cell niche•Lipid droplets protect niche and neural stem cells from damaging PUFA peroxidation•PUFAs are less vulnerable to peroxidation in lipid droplets than in cell membranes
Lipid droplets can act as antioxidant organelles that protect Drosophila neural stem cells from hypoxia-triggered ROS. They sequester polyunsaturated fatty acids away from plasma membranes, thereby shielding these lipids from harmful peroxidation that would otherwise compromise proliferation.
Recently, there has been a growing interest in deploying smart materials as sensing components of structural health monitoring systems. In this arena, piezoelectric materials offer great promise for ...researchers to rapidly expand their many potential applications. The main goal of this study is to review the state-of-the-art piezoelectric-based sensing techniques that are currently used in the structural health monitoring area. These techniques range from piezoelectric electromechanical impedance and ultrasonic Lamb wave methods to a class of cutting-edge self-powered sensing systems. We present the principle of the piezoelectric effect and the underlying mechanisms used by the piezoelectric sensing methods to detect the structural response. Furthermore, the pros and cons of the current methodologies are discussed. In the end, we envision a role of the piezoelectric-based techniques in developing the next-generation self-monitoring and self-powering health monitoring systems.
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