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Dave Keighley, Suporn Boonsue, Douglas Hall
Microscopic globular structures have been observed in some beds of oil shale from eastern Utah. These beds comprise carbonate-dominated mud that is interlaminated with variably thick and continuous organic-rich layers. Collectively they are enriched in phosphorus, REEs, and actinides. The beds are considered of lacustrine origin and assigned to the Eocene Green River Formation. The globules themselves are of microcrystalline carbonate fluorapatite (μCFA), often contain concentric internal structures, and usually group together in clusters of up to 80, possibly more...
August 13, 2018: Geobiology
Erica Victoria Barlow, Martin Julian Van Kranendonk
Eighteen microfossil morphotypes from two distinct facies of black chert from a deep-water setting of the c. 2.4 Ga Turee Creek Group, Western Australia, are reported here. A primarily in situ, deep-water benthic community preserved in nodular black chert occurs as a tangled network of a variety of long filamentous microfossils, unicells of one size distribution and fine filamentous rosettes, together with relatively large spherical aggregates of cells interpreted as in-fallen, likely planktonic, forms. Bedded black cherts, in contrast, preserve microfossils primarily within, but also between, rounded clasts of organic material that are coated by thin, convoluted carbonaceous films interpreted as preserved extracellular polymeric substance (EPS)...
August 9, 2018: Geobiology
Kaarel Mänd, Kalle Kirsimäe, Aivo Lepland, Chris H Crosby, Jake V Bailey, Kurt O Konhauser, Richard Wirth, Anja Schreiber, Kaarel Lumiste
Sedimentary phosphorites comprise a major phosphorus (P) ore, yet their formation remains poorly understood. Extant polyphosphate-metabolizing bacterial communities are known to act as bacterial phosphate-pumps, leading to episodically high dissolved phosphate concentrations in pore waters of organic-rich sediment. These conditions can promote the precipitation of amorphous precursor phases that are quickly converted to apatite-usually in carbonate fluorapatite form [Ca10 (PO4 ,CO3 )6 F2-3 ]. To assess the mechanisms underpinning the nucleation and growth of sedimentary apatite, we sampled P-rich sediments from the Namibian shelf, a modern environment where phosphogenesis presently occurs...
July 30, 2018: Geobiology
Veljo Kisand, Liisi Talas, Anu Kisand, Normunds Stivrins, Triin Reitalu, Tiiu Alliksaar, Jüri Vassiljev, Merlin Liiv, Atko Heinsalu, Heikki Seppä, Siim Veski
Most studies that utilize ancient DNA have focused on specific groups of organisms or even single species. Instead, the whole biodiversity of eukaryotes can be described using universal phylogenetic marker genes found within well-preserved sediment cores that cover the post-glacial period. Sedimentary ancient DNA samples from Lake Lielais Svētiņu, eastern Latvia, at a core depth of 1,050 cm in ~150 year intervals were used to determine phylotaxonomy in domain Eukaryota. Phylotaxonomic affiliation of >1,200 eukaryotic phylotypes revealed high richness in all major eukaryotic groups-Alveolata, Stramenopiles, Cercozoa, Chlorophyta, Charophyta, Nucletmycea, and Holozoa...
July 23, 2018: Geobiology
Melody R Lindsay, Maximiliano J Amenabar, Kristopher M Fecteau, Randal V Debes, Maria C Fernandes Martins, Kirsten E Fristad, Huifang Xu, Tori M Hoehler, Everett L Shock, Eric S Boyd
The geochemistry of hot springs and the availability of oxidants capable of supporting microbial metabolisms are influenced by subsurface processes including the separation of hydrothermal fluids into vapor and liquid phases. Here, we characterized the influence of geochemical variation and oxidant availability on the abundance, composition, and activity of hydrogen (H2 )-dependent chemoautotrophs along the outflow channels of two-paired hot springs in Yellowstone National Park. The hydrothermal fluid at Roadside East (RSE; 82...
July 23, 2018: Geobiology
Tyler B Johnson, Collin Mach, Ryan Grove, Robert Kelly, Kevin Van Cott, Paul Blum
Microbes belonging to the genus Metallosphaera oxidize sulfidic minerals. These organisms thrive at temperature extremes and are members of the archaeal phylum Crenarchaeota. Because they can employ a lithoautotrophic metabolism, energy availability likely limits their activity raising questions about how they conduct biogeochemical activity. Vesicles are membrane encapsulated structures produced by all biological lineages but using very different mechanisms. Across the Crenarchaeota, it has been proposed that a eukaryotic-like Endosomal Sorting Complex Required for Transport system promotes formation of these structures but in response to unknown signals and for undefined purposes...
July 17, 2018: Geobiology
Carl A Peters, Simon C George
Research on the early rise of oxygenic photosynthesis and eukaryotes has recently encountered a major pitfall, as some hopane and sterane biomarkers reported in Archaean rocks are the results of contamination. Following an extensive petrological framework in the Pilbara Craton, Western Australia, oil-bearing fluid inclusions and solid bitumens were identified in replacement and hydrothermal carbonate veins cross-cutting Archaean metasedimentary rocks. The 2.55-2.63 billion years old metasedimentary rocks were found to be depleted of indigenous biomarkers...
July 5, 2018: Geobiology
Henrik Drake, Martin J Whitehouse, Christine Heim, Peter W Reiners, Mikael Tillberg, K Johan Hogmalm, Mark Dopson, Curt Broman, Mats E Åström
In the deep biosphere, microbial sulfate reduction (MSR) is exploited for energy. Here, we show that, in fractured continental crystalline bedrock in three areas in Sweden, this process produced sulfide that reacted with iron to form pyrite extremely enriched in 34 S relative to 32 S. As documented by secondary ion mass spectrometry (SIMS) microanalyses, the δ34 Spyrite values are up to +132‰V-CDT and with a total range of 186‰. The lightest δ34 Spyrite values (-54‰) suggest very large fractionation during MSR from an initial sulfate with δ34 S values (δ34 Ssulfate,0 ) of +14 to +28‰...
June 27, 2018: Geobiology
Jérémie Aubineau, Abderrazak El Albani, Ernest Chi Fru, Murray Gingras, Yann Batonneau, Luis A Buatois, Claude Geffroy, Jérôme Labanowski, Claude Laforest, Laurent Lemée, Maria G Mángano, Alain Meunier, Anne-Catherine Pierson-Wickmann, Philippe Recourt, Armelle Riboulleau, Alain Trentesaux, Kurt O Konhauser
The 2.1-billion-year-old (Ga) Francevillian series in Gabon hosts some of the oldest reported macroscopic fossils of various sizes and shapes, stimulating new debates on the origin, evolution and organization of early complex life. Here, we document ten representative types of exceptionally well-preserved mat-related structures, comprising "elephant-skin" textures, putative macro-tufted microbial mats, domal buildups, flat pyritized structures, discoidal microbial colonies, horizontal mat growth patterns, wrinkle structures, "kinneyia" structures, linear patterns and nodule-like structures...
June 20, 2018: Geobiology
Anne E Otwell, Stephen J Callister, Robert W Sherwood, Sheng Zhang, Abby R Goldman, Richard D Smith, Ruth E Richardson
We established Fe(III)-reducing co-cultures of two species of metal-reducing bacteria, the Gram-positive Desulfotomaculum reducens MI-1 and the Gram-negative Geobacter sulfurreducens PCA. Co-cultures were given pyruvate, a substrate that D. reducens can ferment and use as electron donor for Fe(III) reduction. G. sulfurreducens relied upon products of pyruvate oxidation by D. reducens (acetate, hydrogen) for use as electron donor in the co-culture. Co-cultures reduced Fe(III) to Fe(II) robustly, and Fe(II) was consistently detected earlier in co-cultures than pure cultures...
June 15, 2018: Geobiology
Alexander Brasier, David Wacey, Mike Rogerson, Paul Guagliardo, Martin Saunders, Siri Kellner, Ramon Mercedes-Martin, Tim Prior, Colin Taylor, Anna Matthews, John Reijmer
Lacustrine carbonate chimneys are striking, metre-scale constructions. If these were bioinfluenced constructions, they could be priority targets in the search for early and extraterrestrial microbial life. However, there are questions over whether such chimneys are built on a geobiological framework or are solely abiotic geomorphological features produced by mixing of lake and spring waters. Here, we use correlative microscopy to show that microbes were living around Pleistocene Mono Lake carbonate chimneys during their growth...
June 9, 2018: Geobiology
Claire R Cousins, Marilyn Fogel, Roxane Bowden, Ian Crawford, Adrian Boyce, Charles Cockell, Matthew Gunn
We investigated bacterial and archaeal communities along an ice-fed surficial hot spring at Kverkfjöll volcano-a partially ice-covered basaltic volcano at Vatnajökull glacier, Iceland, using biomolecular (16S rRNA, apsA, mcrA, amoA, nifH genes) and stable isotope techniques. The hot spring environment is characterized by high temperatures and low dissolved oxygen concentrations at the source (68°C and <1 mg/L (±0.1%)) changing to lower temperatures and higher dissolved oxygen downstream (34.7°C and 5...
June 1, 2018: Geobiology
Mario Giordano, Camilla Olivieri, Simona Ratti, Alessandra Norici, John A Raven, Andrew H Knoll
We report the results of simple experiments which support the hypothesis that changes in ocean chemistry beginning in the Mesozoic Era resulted in an increase in the nutritional quality per mole of C and per cell of planktonic algal biomass compared to earlier phytoplankton. We cultured a cyanobacterium, a diatom, a dinoflagellate, and a green alga in media mimicking aspects of the chemistry of Palaeozoic and Mesozoic-Cenozoic oceans. Substantial differences emerged in the quality of algal biomass between the Palaeozoic and Mesozoic-Cenozoic growth regimes; these differences were strongly affected by interspecific interactions (i...
May 30, 2018: Geobiology
Elif Koeksoy, Maximilian Halama, Nikolas Hagemann, Pascal R Weigold, Katja Laufer, Sara Kleindienst, James M Byrne, Anneli Sundman, Kurt Hanselmann, Itay Halevy, Ronny Schoenberg, Kurt O Konhauser, Andreas Kappler
As a consequence of Earth's surface oxygenation, ocean geochemistry changed from ferruginous (iron(II)-rich) into more complex ferro-euxinic (iron(II)-sulphide-rich) conditions during the Paleoproterozoic. This transition must have had profound implications for the Proterozoic microbial community that existed within the ocean water and bottom sediment; in particular, iron-oxidizing bacteria likely had to compete with emerging sulphur-metabolizers. However, the nature of their coexistence and interaction remains speculative...
July 2018: Geobiology
Terry T Isson, Gordon D Love, Christopher L Dupont, Christopher T Reinhard, Alex J Zumberge, Dan Asael, Bleuenn Gueguen, John McCrow, Ben C Gill, Jeremy Owens, Robert H Rainbird, Alan D Rooney, Ming-Yu Zhao, Eva E Stueeken, Kurt O Konhauser, Seth G John, Timothy W Lyons, Noah J Planavsky
The biogeochemical cycling of zinc (Zn) is intimately coupled with organic carbon in the ocean. Based on an extensive new sedimentary Zn isotope record across Earth's history, we provide evidence for a fundamental shift in the marine Zn cycle ~800 million years ago. We discuss a wide range of potential drivers for this transition and propose that, within available constraints, a restructuring of marine ecosystems is the most parsimonious explanation for this shift. Using a global isotope mass balance approach, we show that a change in the organic Zn/C ratio is required to account for observed Zn isotope trends through time...
July 2018: Geobiology
Motoko Igisu, Tadashi Yokoyama, Yuichiro Ueno, Satoru Nakashima, Mie Shimojima, Hiroyuki Ohta, Shigenori Maruyama
Aliphatic C-H bonds are one of the major organic signatures detected in Proterozoic organic microfossils, and their origin is a topic of interest. To investigate the influence of the presence of silica on the thermal alteration of aliphatic C-H bonds in prokaryotic cells during diagenesis, cyanobacteria Synechocystis sp. PCC6803 were heated at temperatures of 250-450°C. Changes in the infrared (IR) signals were monitored by micro-Fourier transform infrared (FTIR) spectroscopy. Micro-FTIR shows that absorbances at 2,925 cm-1 band (aliphatic CH2 ) and 2,960 cm-1 band (aliphatic CH3 ) decrease during heating, indicating loss of the C-H bonds, which was delayed by the presence of silica...
July 2018: Geobiology
K M Sutherland, S D Wankel, C M Hansel
The ability of micro-organisms to oxidize manganese (Mn) from Mn(II) to Mn(III/IV) oxides transcends boundaries of biological clade or domain. Many bacteria and fungi oxidize Mn(II) to Mn(III/IV) oxides directly through enzymatic activity or indirectly through the production of reactive oxygen species. Here, we determine the oxygen isotope fractionation factors associated with Mn(II) oxidation via various biotic (bacteria and fungi) and abiotic Mn(II) reaction pathways. As oxygen in Mn(III/IV) oxides may be derived from precursor water and molecular oxygen, we use a twofold approach to determine the isotope fractionation with respect to each oxygen source...
July 2018: Geobiology
J M Fulton, M A Arthur, B Thomas, K H Freeman
The carbon and nitrogen isotopic signatures of chloropigments and porphyrins from the sediments of redox-stratified lakes and marine basins reveal details of past biogeochemical nutrient cycling. Such interpretations are strengthened by modern calibration studies, and here, we report on the C and N isotopic composition of pigments and nutrients in the water column and surface sediment of redox-stratified Fayetteville Green Lake (FGL; New York). We also report δ13 C and δ15 N values for pyropheophytin a (Pphe a) and bacteriochlorophyll e (Bchl e) deposited in the Black Sea during its transition to a redox-stratified basin ca...
July 2018: Geobiology
A Pace, R Bourillot, A Bouton, E Vennin, O Braissant, C Dupraz, T Duteil, I Bundeleva, P Patrier, S Galaup, Y Yokoyama, M Franceschi, A Virgone, P T Visscher
In modern stromatolites, mineralization results from a complex interplay between microbial metabolisms, the organic matrix, and environmental parameters. Here, we combined biogeochemical, mineralogical, and microscopic analyses with measurements of metabolic activity to characterize the mineralization processes and products in an emergent (<18 months) hypersaline microbial mat. While the nucleation of Mg silicates is ubiquitous in the mat, the initial formation of a Ca-Mg carbonate lamina depends on (i) the creation of a high-pH interface combined with a major change in properties of the exopolymeric substances at the interface of the oxygenic and anoxygenic photoautotrophic layers and (ii) the synergy between two major players of sulfur cycle, purple sulfur bacteria, and sulfate-reducing bacteria...
July 2018: Geobiology
I Hawes, A D Jungblut, E D Matys, R E Summons
The Cryogenian (~717-636 Ma) is characterized by widespread glaciation and dramatic fluctuations in biogeochemical cycling during the Sturtian and Marinoan glaciations. The Snowball Earth hypothesis posits that during this period, ice-covered oceans of more or less global extent shut down or greatly diminished photosynthesis in the marine realm. However, rather than suffering a catastrophic loss of biodiversity, fossil evidence suggests that major eukaryotic lineages survived and, indeed, the end of the Cryogenian marks the onset of a rapid diversification of eukaryotic life...
July 2018: Geobiology
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