137 research outputs found
Does the primary deposit affect the biogeochemical transformation of placer gold and associated biofilms?
No full textAbstract not availableMaria Angelica Rea, Jeremiah Shuster, Veit E. Hoffmann, Markus Schade, Andrew Bissett, Frank Reit
Effect of physical and biogeochemical factors on placer gold transformation in mountainous landscapes of Switzerland
No full textAbstract not availableMaria Angelica D. Rea, Pierre-Alain Wulser, Joël Brugger, Barbara Etschmann, Andrew Bissett, Jeremiah Shuster, Frank Reit
Progressive biogeochemical transformation of placer gold particles drives compositional changes in associated biofilm communities
No full textBiofilms on placer gold (Au)-particle surfaces drive Au solubilization and re-concentration thereby progressively transforming the particles. Gold solubilization induces Au-toxicity; however, Au-detoxifying community members ameliorates Au-toxicity by precipitating soluble Au to metallic Au. We hypothesize that Au-dissolution and re-concentration (precipitation) places selective pressures on associated microbial communities, leading to compositional changes and subsequent Au-particle transformation. We analyzed Au-particles from eight United Kingdom sites using next generation sequencing, electron microscopy and micro-analyses. Gold particles contained biofilms composed of prokaryotic cells and extracellular polymeric substances intermixed with (bio)minerals. Across all sites communities were dominated by Proteobacteria (689, 97% Operational Taxonomic Units, 59.3% of total reads), with β-Proteobacteria being the most abundant. A wide range of Au-morphotypes including nanoparticles, micro-crystals, sheet-like Au and secondary rims, indicated that dissolution and re-precipitation occurred, and from this transformation indices were calculated. Multivariate statistical analyses showed a significant relationship between the extent of Au-particle transformation and biofilm community composition, with putative metal-resistant Au-cycling taxa linked to progressive Au transformation. These included the genera Pseudomonas, Leptothrix and Acinetobacter. Additionally, putative exoelectrogenic genera Rhodoferax and Geobacter were highly abundant. In conclusion, biogeochemical Au-cycling and Au-particle transformation occurred at all sites and exerted a strong influence on biofilm community composition
Hydrothermal sulfidation of biogenic magnetite produces framboid-like pyrite
No full text<jats:title>Abstract</jats:title><jats:p>Biogenic magnetite is a potential biosignature for microbial iron cycling in hydrothermal sulfide systems, critical environments for unraveling the emergence and early evolution of life. However, the preservation potential of biogenic magnetite under hydrothermal conditions is poorly understood. Here, we show that the hydrothermal sulfidation of abiogenic and biogenic magnetite (sulfide/iron = 4, 80 °C) yields pyrite with various distinct morphologies, including framboid-like spheroids. We demonstrate that the variability in pyrite morphologies resulted from the modulation of pyritization rates by interrelated effects between organic matter and elemental sulfur (crystalline or colloidal). Notably, framboid-like pyrite, commonly considered a potential fingerprint of microbial sulfur cycling, was exclusively produced from the hydrothermal sulfidation of biogenic (i.e., organic matter-associated) magnetite produced by iron-cycling microorganisms. Thus, framboid-like pyrite can additionally be a taphonomic fingerprint of microbial iron cycling, enabling a better understanding of the evolution of Earth’s biosphere in deep time.</jats:p>
Editorial for special issue "geomicrobiology and biogeochemistry of precious metals"
No full textn/aFrank Reith and Jeremiah Shuste
Sulfidation of nano-magnetite to pyrite: Implications for interpreting paleoenvironmental proxies and biosignature records in hydrothermal sulfide deposits
No full textThe quest for Brazilian space research
No full textThis paper describes how QUEST(1) (QUaternion ESTimator algorithm) influenced Brazilian space research activities. Indeed, we present a short survey paper on researches in attitude determination and propagation in Brazil arising from the influence of the author of QUEST. We show how Brazilian researchers started implementing QUEST, tasting it, and later deriving other applications based on it. Some Brazilian researchers worked out further investigations through direct interaction with the QUEST author, Dr. Malcolm Shuster, addressing attitude alignment and calibration problems. Further related researches show the influence of Dr. Shuster's work on Brazilian space research.Inst Nacl Pesquisas Espaciais, POB 515, BR-12245970 Sao Jose Dos Campos, SP, BrazilSao Paulo State Univ, UNESP, Dept Math, BR-12500000 Guaratingueta, SP, BrazilSao Paulo State Univ, UNESP, Dept Math, BR-12500000 Guaratingueta, SP, Brazi
Impact of silica on the identity of minerals formed in Archean oceans during Fe cycling by cyanobacteria and iron(III)-reducing bacteria
No full textWzajemność i międzypodmiotowy dialog w edukacji religijnej
No full textIntentional mutuality and intersubjective dialogue woven into the pedagogy of youth and adults is a radical idea in any educational setting; however in the case of religious education it can provide a generative, hermeneutic, learning platform for the development of Christocentric living (as one example). Through so doing, this learning platform can easily extend into the postmodern secular sphere to temper and balance its epistemic forms with hermeneutics, ethics, empathy, and social justice. Where religious education can remain free of the control of neoliberal ideology, it can help students flourish in their humanity and agency. At the same time, religious education and critical pedagogies can be further developed on the shoulders of their giants with gleanings from the secular world—practices and methods from a range of human traditions. In that spirit, the author borrows substantial elements from his previous work (Shuster 2006) on the effectiveness of dialogue and intersubjectivity in postmodern workgroups and speculates on its utility to learning groups and classrooms.Celowa wzajemność i międzypodmiotowy dialog, wplecione w pedagogię młodzieży i dorosłych, stanowi radykalną ideę w dziedzinie edukacji. W przypadku edukacji religijnej może to oznaczać organizację generatywnej i hermeneutycznej platformy nauczania, służącej rozwijaniu chrystocentrycznego modelu życia (jako jednego z przykładów). W ten sposób platforma ta może łatwo się rozszerzać, wkraczając na obszar ponowoczesny i świecki, łagodząc i równoważąc przy tym jego epistemiczne formy hermeneutyką, etyką, empatią i sprawiedliwością społeczną. Tam, gdzie edukacja religijna pozostaje wolna od kontroli ze strony neoliberalnej ideologii, tam może pomóc uczniom w rozwoju ich człowieczeństwa i aktywności. W tym samym czasie edukacja religijna oraz krytycznie ukierunkowane pedagogie mogą być rozwijane przez ich głównych orędowników, zbierając przy tym doświadczenia również ze świeckiego świata, tj. praktyki i metody reprezentujące rozmaite tradycje. Podążając za tym przykładem, autor przejmuje znaczące elementy ze swej wcześniejszej pracy (Shuster 2006) na temat skuteczności dialogu i międzypodmiotowości w ponowoczesnych grupach pracowniczych i zastanawia się nad ich przydatnością w grupach osób uczących się oraz podczas zajęć w klasie szkolnej
Reflecting on gold geomicrobiology research: thoughts and considerations for future endeavors
No full textResearch in gold (Au) geomicrobiology has developed extensively over the last ten years, as more Au-bearing materials from around the world point towards a consistent story: That microbes interact with Au. In weathering environments, Au is mobile, taking the form of oxidized, soluble complexes or reduced, elemental Au nanoparticles. The transition of Au between aqueous and solid states is attributed to varying geochemical conditions, catalyzed in part by the biosphere. Hence, a global Au-biogeochemical-cycle was proposed. The primary focus of this mini-review is to reflect upon the biogeochemical processes that contribute to what we currently know about Au cycling. In general, the global Au-biogeochemical-cycle begins with the liberation of gold-silver particles from a primary host rock, by physical weathering. Through oxidative-complexation, inorganic and organic soluble-Au complexes are produced. However, in the presence of microbes or other reductants—e.g., clays and Fe-oxides—these Au complexes can be destabilized. The reduction of soluble Au ultimately leads to the bioprecipitation and biomineralization of Au, the product of which can aggregate into larger structures, thereby completing the Au cycle. Evidence of these processes have been “recorded” in the preservation of secondary Au structures that have been observed on Au particles from around the world. These structures—i.e., nanometer-size to micrometer-size Au dissolution and reprecipitation features—are “snap shots” of biogeochemical influences on Au, during its journey in Earth-surface environments. Therefore, microbes can have a profound effect on the occurrence of Au in natural environments, given the nutrients necessary for microbial metabolism are sustained and Au is in the system.Jeremiah Shuster and Frank Reit
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