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  • 1. Bengtson, S.
    et al.
    Ivarsson, M.
    Astolfo, A.
    Belivanova, V.
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Marone, F.
    Stampanoni, M.
    Deep-biosphere consortium of fungi and prokaryotes in Eocene subseafloor basalts2014In: Geobiology, ISSN 1472-4677, E-ISSN 1472-4669, Vol. 12, no 6, p. 489-496Article in journal (Refereed)
    Abstract [en]

    The deep biosphere of the subseafloor crust is believed to contain a significant part of Earth's biomass, but because of the difficulties of directly observing the living organisms, its composition and ecology are poorly known. We report here a consortium of fossilized prokaryotic and eukaryotic micro-organisms, occupying cavities in deep-drilled vesicular basalt from the Emperor Seamounts, Pacific Ocean, 67.5m below seafloor (mbsf). Fungal hyphae provide the framework on which prokaryote-like organisms are suspended like cobwebs and iron-oxidizing bacteria form microstromatolites (Frutexites). The spatial inter-relationships show that the organisms were living at the same time in an integrated fashion, suggesting symbiotic interdependence. The community is contemporaneous with secondary mineralizations of calcite partly filling the cavities. The fungal hyphae frequently extend into the calcite, indicating that they were able to bore into the substrate through mineral dissolution. A symbiotic relationship with chemoautotrophs, as inferred for the observed consortium, may be a pre-requisite for the eukaryotic colonization of crustal rocks. Fossils thus open a window to the extant as well as the ancient deep biosphere.

  • 2.
    Chi Fru, Ernest
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences. Swedish Museum of Natural History, Sweden.
    Ivarsson, M.
    Kilias, S. P.
    Frings, P. J.
    Hemmingsson, Christoffer
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Bengtson, S.
    Chatzitheodoridis, E.
    Biogenicity of an Early Quaternary iron formation, Milos Island, Greece2015In: Geobiology, ISSN 1472-4677, E-ISSN 1472-4669, Vol. 13, no 3, p. 225-244Article in journal (Refereed)
    Abstract [en]

    A 2.0-million-year-old shallow-submarine sedimentary deposit on Milos Island, Greece, harbours an unmetamorphosed fossiliferous iron formation (IF) comparable to Precambrian banded iron formations (BIFs). This Milos IF holds the potential to provide clues to the origin of Precambrian BIFs, relative to biotic and abiotic processes. Here, we combine field stratigraphic observations, stable isotopes of C, S and Si, rock petrography and microfossil evidence from a 5-m-thick outcrop to track potential biogeochemical processes that may have contributed to the formation of the BIF-type rocks and the abrupt transition to an overlying conglomerate-hosted IF (CIF). Bulk C-13 isotopic compositions lower than -25 parts per thousand provide evidence for biological contribution by the Calvin and reductive acetyl-CoA carbon fixation cycles to the origin of both the BIF-type and CIF strata. Low S levels of 0.04 wt.% combined with S-34 estimates of up to 18 parts per thousand point to a non-sulphidic depository. Positive Si-30 records of up to +0.53 parts per thousand in the finely laminated BIF-type rocks indicate chemical deposition on the seafloor during weak periods of arc magmatism. Negative Si-30 data are consistent with geological observations suggesting a sudden change to intense arc volcanism potentially terminated the deposition of the BIF-type layer. The typical Precambrian rhythmic rocks of alternating Fe- and Si-rich bands are associated with abundant and spatially distinct microbial fossil assemblages. Together with previously proposed anoxygenic photoferrotrophic iron cycling and low sedimentary N and C potentially connected to diagenetic denitrification, the Milos IF is a biogenic submarine volcano-sedimentary IF showing depositional conditions analogous to Archaean Algoma-type BIFs.

  • 3. Drake, Henrik
    et al.
    Whitehouse, Martin J.
    Heim, Christine
    Reiners, Peter W.
    Tillberg, Mikael
    Hogmalm, K. Johan
    Dopson, Mark
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Åstrom, Mats E.
    Unprecedented S-34-enrichment of pyrite formed following microbial sulfate reduction in fractured crystalline rocks2018In: Geobiology, ISSN 1472-4677, E-ISSN 1472-4669, Vol. 16, no 5, p. 556-574Article in journal (Refereed)
    Abstract [en]

    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 S-34 relative to S-32. As documented by secondary ion mass spectrometry (SIMS) microanalyses, the S-34(pyrite) values are up to +132 parts per thousand V-CDT and with a total range of 186 parts per thousand. The lightest S-34(pyrite) values (-54 parts per thousand) suggest very large fractionation during MSR from an initial sulfate with S-34 values (S-34(sulfate,0)) of +14 to +28 parts per thousand. Fractionation of this magnitude requires a slow MSR rate, a feature we attribute to nutrient and electron donor shortage as well as initial sulfate abundance. The superheavy S-34(pyrite) values were produced by Rayleigh fractionation effects in a diminishing sulfate pool. Large volumes of pyrite with superheavy values (+120 +/- 15 parts per thousand) within single fracture intercepts in the boreholes, associated heavy average values up to +75 parts per thousand and heavy minimum S-34(pyrite) values, suggest isolation of significant amounts of isotopically light sulfide in other parts of the fracture system. Large fracture-specific S-34(pyrite) variability and overall average S-34(pyrite) values (+11 to +16 parts per thousand) lower than the anticipated S-34(sulfate,0) support this hypothesis. The superheavy pyrite found locally in the borehole intercepts thus represents a late stage in a much larger fracture system undergoing Rayleigh fractionation. Microscale Rb-Sr dating and U/Th-He dating of cogenetic minerals reveal that most pyrite formed in the early Paleozoic era, but crystal overgrowths may be significantly younger. The C-13 values in cogenetic calcite suggest that the superheavy S-34(pyrite) values are related to organotrophic MSR, in contrast to findings from marine sediments where superheavy pyrite has been proposed to be linked to anaerobic oxidation of methane. The findings provide new insights into MSR-related S-isotope systematics, particularly regarding formation of large fractions of S-34-rich pyrite.

  • 4.
    Edberg, Frida
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Kalinowski, Birgitta E..
    Swedish Nuclear Fuel and Waste Mangament Co, Stockholm .
    Holmström, Sara J. M.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Holm, Karin
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Mobilization of metals from uranium mine waste: the role of pyoverdines produced by Pseudomonas fluorescens2010In: Geobiology, ISSN 1472-4677, E-ISSN 1472-4669, Vol. 8, no 4, p. 278-292Article in journal (Refereed)
    Abstract [en]

    Microorganisms produce chelating agents, such as siderophores and other ligands, which allow them to mobilize and scavenge essential elements from the environment when bioavailability is low. To better understand the effects of biologically mediated leaching of metals from mine waste, Pseudomonas fluorescens was cultivated in the presence of processed ore from the former uranium mine in Ranstad, southern Sweden. Light conditions, the concentration of the mineral source and oxygen availability were varied. The presence of ore in the culture flasks enhanced bacterial growth and raised the pH of the culture medium. Increasing the amount of ore or enhancing aeration of the medium further encouraged cell growth and pH rise. Bacteria mobilized Fe, Ni and Co from the ore. Fe-siderophore complexes were detected and estimated to be present at approximately 9 μm. In the presence of bacteria and light, dissolved Fe and U concentrations were higher compared to dark conditions. Increasing the amount of ore resulted in higher dissolved Ni concentrations but lower dissolved Fe, most likely due to precipitate formation. Data from this study support siderophore production by bacteria that allowed mobilization of essential nutrients from the processed ore. However, the availability of potentially toxic metals like Ni and U may also be enhanced. Microbial-promoted mobilization could contribute to leaching of toxic metals in current and historic mining areas. This process should be considered during design and implementation of remediation projects where trace metals are of environmental concern.

  • 5.
    Holm, Nils G.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    The significance of Mg in prebiotic geochemistry2012In: Geobiology, ISSN 1472-4677, E-ISSN 1472-4669, Vol. 10, no 4, p. 269-279Article, review/survey (Refereed)
    Abstract [en]

    Magnesium plays a special role in biochemistry because of its ability to coordinate six oxygen atoms efficiently in its first coordination shell. Such oxygen atoms may be part of one or two charged oxyanions, which means that Mg2+ can, for instance, tie together two different phosphate groups that are located at distance from each other in a macromolecule, and in this way be responsible for the folding of molecules like RNA. This property of Mg2+ also helps the stabilization of diphosphate and triphosphate groups of nucleotides, as well as promoting the condensation of orthophosphate to oligophosphates, like pyrophosphate and trimetaphosphate. Borates, on the other hand, are known to promote the formation of nucleobases and carbohydrates, ribose in particular, which is yet another constituent of nucleotides. The oldest borate minerals that we find on Earth today are magnesium borates. Dissolved borate stabilizes pentose sugars by forming complexes with cis-hydroxyl groups. In the furanose form of ribose, the preferential binding occurs to the 2 and 3 carbon, leaving the 5 carbon free for phosphorylation. The central role of Mg2+ in the function of ribozymes and its archaic position in ribosomes, and the fact that magnesium generally has coordination properties different from other cations, suggests that the inorganic chemistry of magnesium had a key position in the first chemical processes leading to the origin and early evolution of life.

  • 6.
    Ivarsson, Magnus
    et al.
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Lindblom, Sten
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Broman, Curt
    Naturhistoriska riksmuseet.
    Holm, Nils
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Fossilized microorganisms associated with zeolite-carbonate interfaces in sub-seafloor hydrothermal environments2008In: Geobiology, ISSN 1472-4677, E-ISSN 1472-4669, Vol. 6, no 2, p. 155-170Article in journal (Refereed)
    Abstract [en]

    In this paper we describe carbon-rich filamentous structures observed in association with the zeolite mineral phillipsite from sub-seafloor samples drilled and collected during the Ocean Drilling Program (ODP) Leg 197 at the Emperor Seamounts. The filamentous structures are ~5 µm thick and ~100–200 µm in length. They are found attached to phillipsite surfaces in veins and entombed in vein-filling carbonates. The carbon content of the filaments ranges between ~10 wt% C and 55 wt% C. They further bind to propidium iodide (PI), which is a dye that binds to damaged cell membranes and remnants of DNA.

    Carbon-rich globular microstructures, 1–2 µm in diameter, are also found associated with the phillipsite surfaces as well as within wedge-shaped cavities in phillipsite assemblages. The globules have a carbon content that range between ~5 wt% C and 55 wt% C and they bind to PI. Ordinary globular iron oxides found throughout the samples differ in that they contain no carbon and do not bind to the dye PI. The carbon-rich globules are mostly concentrated to a film-like structure that is attached to the phillipsite surfaces. This film has a carbon content that ranges between ~25 wt% C and 75 wt% C and partially binds to PI. EDS analyses show that the carbon in all structures described are not associated with calcium and therefore not bound in carbonates. The carbon content and the binding to PI may indicate that the filamentous structures could represent fossilized filamentous microorganisms, the globules could represent fossilized microbial cells and the film-like structures could represent a microbially produced biofilm.

    Our results extend the knowledge of possible habitable niches for a deep biosphere in sub-seafloor environments and suggests, as phillipsite is one of the most common zeolite mineral in volcanic rocks of the oceanic crust, that it could be a common feature in the oceanic crust elsewhere.

  • 7. Konn, C.
    et al.
    Testemale, D.
    Querellou, J.
    Holm, Nils G.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Charlou, J. L.
    New insight into the contributions of thermogenic processes and biogenic sources to the generation of organic compounds in hydrothermal fluids2011In: Geobiology, ISSN 1472-4677, E-ISSN 1472-4669, Vol. 9, no 1, p. 79-93Article in journal (Refereed)
    Abstract [en]

    Experiments on hydrothermal degradation of Pyrococcus abyssi biomass were conducted at elevated pressure (40 MPa) over a 200–450 °C temperature range in sapphire reaction cells. Few organic compounds could be detected in the 200 °C experiment. This lack was attributed to an incomplete degradation of P. abyssi cells. On the contrary, a wide range of soluble organic molecules were generated at temperatures ≥350 °C including toluene, styrene, C8–C16 alkyl-benzenes, naphthalene, C11–C16 alkyl-naphthalenes, even carbon number C12–C18 polycyclic aromatic hydrocarbons, C15–C18 alkyl-phenanthrenes and C8:0–C16:0 n-carboxylic acids. The effect of time on the final organic composition of the degraded P. abyssi solutions at 350 °C was also investigated. For that purpose the biomass was exposed for 10, 20, 60, 90, 270 and 720 min at 350 °C. We observed a similar effect of temperature and time on the chemical diversity obtained. In addition, temperature and time increased the degree of alkylation of alkyl-benzenes. This study offers additional evidence that a portion of the aliphatic hydrocarbons present in the fluids from the Rainbow ultramafic-hosted hydrothermal field may be abiogenic whereas a portion of the aromatic hydrocarbons and n-carboxylic acids may have a biogenic origin. We suggest that aromatic hydrocarbons and linear fatty acids at the Rainbow site may be derived directly from thermogenic alteration of material from the sub-seafloor biosphere. Yet we infer that the formation and dissolution of carboxylic acids in hydrothermal fluids may be controlled by other processes than in our experiments.

  • 8. Pace, A.
    et al.
    Bourillot, R.
    Bouton, A.
    Vennin, E.
    Braissant, O.
    Dupraz, Christophe
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Duteil, T.
    Bundeleva, I.
    Patrier, P.
    Galaup, S.
    Yokoyama, Y.
    Franceschi, M.
    Virgone, A.
    Visscher, P. T.
    Formation of stromatolite lamina at the interface of oxygenic-anoxygenic photosynthesis2018In: Geobiology, ISSN 1472-4677, E-ISSN 1472-4669, Vol. 16, no 4, p. 378-398Article in journal (Refereed)
    Abstract [en]

    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 (<18months) 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. The repetition of this process over time combined with upward growth of the mat is a possible pathway leading to the formation of a stromatolite.

  • 9. Sallstedt, T.
    et al.
    Bengtson, S.
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Crill, Patrick M.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Canfield, D. E.
    Evidence of oxygenic phototrophy in ancient phosphatic stromatolites from the Paleoproterozoic Vindhyan and Aravalli Supergroups, India2018In: Geobiology, ISSN 1472-4677, E-ISSN 1472-4669, Vol. 16, no 2, p. 139-159Article in journal (Refereed)
    Abstract [en]

    Fossil microbiotas are rare in the early rock record, limiting the type of ecological information extractable from ancient microbialites. In the absence of body fossils, emphasis may instead be given to microbially derived features, such as microbialite growth patterns, microbial mat morphologies, and the presence of fossilized gas bubbles in lithified mats. The metabolic affinity of micro-organisms associated with phosphatization may reveal important clues to the nature and accretion of apatite-rich microbialites. Stromatolites from the 1.6Ga Chitrakoot Formation (Semri Group, Vindhyan Supergroup) in central India contain abundant fossilized bubbles interspersed within fine-grained in situ-precipitated apatite mats with average C-13(org) indicative of carbon fixation by the Calvin cycle. In addition, the mats hold a synsedimentary fossil biota characteristic of cyanobacterial and rhodophyte morphotypes. Phosphatic oncoid cone-like stromatolites from the Paleoproterozoic Aravalli Supergroup (Jhamarkotra Formation) comprise abundant mineralized bubbles enmeshed within tufted filamentous mat fabrics. Construction of these tufts is considered to be the result of filamentous bacteria gliding within microbial mats, and as fossilized bubbles within pristine mat laminae can be used as a proxy for oxygenic phototrophy, this provides a strong indication for cyanobacterial activity in the Aravalli mounds. We suggest that the activity of oxygenic phototrophs may have been significant for the formation of apatite in both Vindhyan and Aravalli stromatolites, mainly by concentrating phosphate and creating steep diurnal redox gradients within mat pore spaces, promoting apatite precipitation. The presence in the Indian stromatolites of alternating apatite-carbonate lamina may result from local variations in pH and oxygen levels caused by photosynthesis-respiration in the mats. Altogether, this study presents new insights into the ecology of ancient phosphatic stromatolites and warrants further exploration into the role of oxygen-producing biotas in the formation of Paleoproterozoic shallow-basin phosphorites.

  • 10. Sforna, M. C.
    et al.
    Daye, M.
    Philippot, P.
    Somogyi, A.
    van Zuilen, M. A.
    Medjoubi, K.
    Gérard, E.
    Jamme, F.
    Dupraz, Christophe
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Braissant, O.
    Glunk, C.
    Visscher, P. T.
    Patterns of metal distribution in hypersaline microbialites during early diagenesis: Implications for the fossil record2017In: Geobiology, ISSN 1472-4677, E-ISSN 1472-4669, Vol. 15, no 2, p. 259-279Article in journal (Refereed)
    Abstract [en]

    The use of metals as biosignatures in the fossil stromatolite record requires understanding of the processes controlling the initial metal(loid) incorporation and diagenetic preservation in living microbialites. Here, we report the distribution of metals and the organic fraction within the lithifying microbialite of the hypersaline Big Pond Lake (Bahamas). Using synchrotron-based X-ray microfluorescence, confocal, and biphoton microscopies at different scales (cm-m) in combination with traditional geochemical analyses, we show that the initial cation sorption at the surface of an active microbialite is governed by passive binding to the organic matrix, resulting in a homogeneous metal distribution. During early diagenesis, the metabolic activity in deeper microbialite layers slows down and the distribution of the metals becomes progressively heterogeneous, resulting from remobilization and concentration as metal(loid)-enriched sulfides, which are aligned with the lamination of the microbialite. In addition, we were able to identify globules containing significant Mn, Cu, Zn, and As enrichments potentially produced through microbial activity. The similarity of the metal(loid) distributions observed in the Big Pond microbialite to those observed in the Archean stromatolites of Tumbiana provides the foundation for a conceptual model of the evolution of the metal distribution through initial growth, early diagenesis, and fossilization of a microbialite, with a potential application to the fossil record.

  • 11.
    Siljeström, Sandra
    et al.
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Lausmaa, Jukka
    Sjövall, Peter
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Thiel, Volker
    Hode, Tomas
    Analysis of hopanes and steranes in single oil-bearing fluid inclusions using time-of-flight secondary ion mass spectrometry (ToF-SIMS)2010In: Geobiology, ISSN 1472-4677, E-ISSN 1472-4669, Vol. 8, no 1, p. 37-44Article in journal (Refereed)
    Abstract [en]

    Steranes and hopanes are organic biomarkers used as indicators for the first appearance of eukaryotes and cyanobacteria on Earth. Oil-bearing fluid inclusions may provide a contamination-free source of Precambrian biomarkers, as the oil has been secluded from the environment since the formation of the inclusion. However, analysis of biomarkers in single oil-bearing fluid inclusions, which is often necessary due to the presence of different generations of inclusions, has not been possible due to the small size of most inclusions. Here, we have used time-of-flight secondary ion mass spectrometry (ToF-SIMS) to monitor in real time the opening of individualinclusions trapped in hydrothermal veins of fluorite and calcite and containing oil from Ordovician source rocks. Opening of the inclusions was performed by using a focused C60+ ion beam and the in situ content was preciselyanalysed for C27–C29 steranes and C29–C32 hopanes using Bi3+ as primary ions. The capacity to unambiguouslydetect these biomarkers in the picoliter amount of crude oil from a single, normal-sized (15–30 µm in diameter)inclusion makes the approach promising in the search of organic biomarkers for life’s early evolution on Earth.

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